Optical parts coupling structure, method of manufacturing the same, optical switch, two-dimensional lens array, and method of manufacturing the same

ABSTRACT

A first optical waveguide having at least a core layer with a refractive index ncj and a second optical waveguide having at least a core layer with a refractive index nck are arranged to oppose their end surfaces, and at least any one end surface of the first optical waveguide and the second optical waveguide is formed by the etching, and the end surface formed by the etching is covered with a coating medium with a refractive index nij or nik that is equal to a refractive index ncj or nck of the core layer that is exposed from the end surface.

This application is a divisional application of prior application Ser.No. 10/446,834, filed on May 29, 2003.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims priority of Japanese PatentApplications No. 2002-159447, filed on May 31, 2002, and No.2002-194030, filed on Jul. 3, 2002, the contents being incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a coupling structural body of opticalparts, a method of manufacturing the same, and an optical switch moduleand, more particularly, a coupling structural body of optical parts suchas an optical propagation system, an image forming system, and anoptical deflecting system employed in an optical signal switching system(switching device, optical signal cross-connecting device) arranged atcross points of an optical network, a method of manufacturing the same,and an optical switch module.

The present invention relates to a two-dimensional lens array having aplurality of two-dimensional lenses each executes collimation orconvergence of an optical signal propagated through a two-dimensionaloptical waveguide, an optical switch having this two-dimensional lensarray, and a method of manufacturing the two-dimensional lens array.

2. Description of the Prior Art

The transmission band in the optical communication keeps on widening inrecent years, and the higher speed and the larger capacity of theoptical communication are advanced with the progress of the wavelengthmultiplexing technology. In order to establish the optical fiber networkin the trunk communication network, the device for switching thedestination of the optical signal is required.

The mainstream of such switching device was the optical cross-connectingdevice having an operation mode such that an optical signal is convertedinto an electric signal once, then the connection is switched in thestate of the electric signal, and then the electric signal is convertedinto the optical signal once again. The electric switch such as acrossbar switch constructed by electronic switches, or the like wasemployed for switching in the state of the electric signal. However,when a data communication rate exceeds 10 Gb/s, it becomes difficult toswitch the connection by using the electric switch.

If the optical switch that can switch directly the light propagationpath is used in place of the electric switch to eliminate thephoto-electric conversion, switching of the optical signal that does notdepends on a rate (frequency) of the optical signal can be implemented.For this reason, there is a tendency such that the opticalcross-connecting device using the optical switches is developed.

In the matrix-switch that employs the 2×2 switch as the base, anabsolute value of loss and variation between ports become a problem ifthe number of ports is increased. Therefore, the analog opticaldeflection type switch, which has a small optical loss between paths, ispreferable. More particularly, the switch of the optical beam switchingtype that employs the deflection by the micromirror can be used. Thereis the switch in which the micromirrors are integrated threedimensionally by using MEMS (microelectromechanical system) technology.

However, according to the optical switch in the MEMS technology, a sizeis large even in a 32×32 scale and a module size including the opticalinput/output port (fiber connector) becomes several tens cm square.

Meanwhile, if a plurality of m×n optical switches that are formed on atwo-dimensional substrate are arranged to construct an optical switchgroup having a two-dimensional optical input/output port arrangement, amodule size can be remarkably reduced into a small scale.

Therefore, a method of constructing the optical switch group on thetwo-dimensional substrate is promising for the optical cross-connectingswitch.

The optical switch module constituting the optical switch group on thetwo-dimensional substrate is composed of optical parts such as a channelwaveguide, a two-dimensional lens, an optical deflector element, etc.Each optical part is constructed by laminating an underlying claddinglayer, a core layer, and an overlying cladding layer on a quartzsubstrate, and then patterning the core layer into a desired shape. Thecore layer constitutes a slab waveguide serving as a main opticalwaveguide, and causes a light to propagate in a flat plane.

In case the optical parts are to be arranged on the substrate, the lightthat is propagated through the optical waveguide must be opticallycoupled between the optical parts. Hence, the core layers of respectiveoptical parts are opposed to each other in the coupling portion betweenthe optical parts while an air layer is put therebetween.

However, in the coupling portion, which has the two-dimensional lens,out of the coupling portions between the optical parts, the light thatis propagated through the optical waveguide must be collimatedtwo-dimensionally and then coupled optically to the slab waveguide. Inthis case, there is the problem such that it is difficult to couple thelight to the slab waveguide at a high efficiency.

This situation will be explained in detail. If the light is coupledoptically by using the conventional two-dimensional lens, the air layeris interposed (in opposing portions) between the two-dimensional lens asthe coupling portion and the slab waveguide. Thus, since the emittedlight is converged in the in-plane direction but such light is divergedin the out-plane direction, a coupling efficiency is lowered. Also, aloss due to the reflection is increased by an increased difference inthe refractive index between inside of the two-dimensional lens andoutside thereof at the end surface thereof.

In order to overcome this problem, the prior application (PatentApplication No. 2001-332169) filed by the same applicant as thisapplication describes an example such that the resin of which therefractive index is larger than that of the atmosphere is buried in theopposing portion. According to this, first the filling resin film isformed by the patterning, and then a resin film to form the core layersis formed thereon, followed by polishing the resin film to form the corelayers so as to planarize a surface thereof. It results in formation ofthe core layers putting the filling resin film therebetween. However,according to this forming method, the manufacturing steps becomecomplicated and also control of a polished amount is needed.

The optical signal is suitable for the high-speed/large-capacity signaltransmission. In the long-haul trunk communication system, the signaltransmission using the optical signal has already been put intopractical use. The optical switch for switching the transmission routeof the optical signal is indispensable in such system. As the approachof implementing this optical switch, various systems have been proposed.In this case, for example, the optical switch using the opticaldeflector element is expected to bring the high-speed switchingoperation. Such optical deflector element is provided with the crystal,as the optical waveguide, having an electro-optical effect such that therefractive index is changed by the electric field. Prism-like electrodesare formed on and under the optical waveguide, and deflect the lightthat is propagated through the optical waveguide by the voltage appliedto the electrodes.

FIGS. 1A and 1B are views showing an example of a configuration of apart of the optical switch using the optical deflector element in theprior art. FIG. 1A is a plan view showing a part of the optical switch,and FIG. 1B is a sectional view taken along a XI—XI line in FIG. 1A.

FIGS. 1A and 1B show, as an example, input-side constituent elements ofan optical switch 800 having 8 input channels. The optical switch 800 onthe input side is provided with an optical input waveguide portion 820,a collimator portion 830, and an optical deflector element portion 840.The optical switch 800 on the output side is provided with a commonoptical waveguide 850. In this optical switch 800, for example, theoptical input waveguide portion 820, the collimator portion 830, and thecommon optical waveguide 850 are provided integrally on a commonsubstrate 801, and then the optical deflector element portion 840 ismounted on this substrate 801.

A plurality of optical input waveguides 821, each corresponds to eachinput channel, are formed in the optical input waveguide portion 820. Anoptical fiber, or the like, for example, is connected to an incident endof each optical input waveguide 821. The optical signals are incident onthe optical fibers respectively.

A plurality of collimator lenses 831, each corresponds to each opticalinput waveguide 821, are formed in the collimator portion 830. Eachcollimator lens 831 has a waveguide layer 832 as the slab opticalwaveguide on which the optical signal is incident from the optical inputwaveguide 821, and an air-gap filling layer 833 which is formed of themedium being different from the waveguide layer 832 in the refractiveindex. In the air-gap filling layer 833, an air-gap region that passesthrough the core layer and overlying/underlying cladding layers in thewaveguide layer 832 is filled with a fluororesin, or the like to preventthe diffusion of light, for example. Then, an end surface of thewaveguide layer 832 opposing to the air-gap filling layer 833 is shapedinto a circular cylindrical surface, for example, to constitute a lenscurved surface 834 of the two-dimensional lens. According to suchstructure, in each collimator lens 831, the optical signal that ispropagated from the optical input waveguide 821 to spread radially inthe waveguide layer 832 is converted in the parallel light by the lenscurved surface 834, and then is emitted to the optical deflector elementportion 840.

A plurality of optical deflector elements 841, each corresponds to theinput channel, are provided in the optical deflector element portion840. In each optical deflector element 841, the refractive index in aslab optical waveguide 842 is changed when the voltages is applied tothe slab optical waveguide 842, which is made of the material having theelectro-optical effect, via a prism-type electrode 843 serving as alower electrode and a conductive substrate 844 serving as an upperelectrode. Thus, the propagation direction of the incident opticalsignal is changed.

The common optical waveguide 850 is the slab optical waveguide whichpropagates commonly all optical signals, of which the connection isswitched between the channels on the input and output sides. The commonoptical waveguide 850 transmits the optical signal that passes throughthe optical deflector element portion 840 to the output side.

In this case, the common optical waveguide 850 on the output side areprovided with the constituent elements that are similar to the opticalinput waveguide portion 820, the collimator portion 830, and the opticaldeflector element portion 840, as shown in FIGS. 1A and 1B, in theopposite direction to the common optical waveguide 850. In other words,the common optical waveguide 850 on the output side is provided withoutput-side optical deflector element portion, light converging portion,and optical output waveguide portion. Those portions have the pluraloptical deflector elements, the plural light converging lenses, and theplural optical output waveguides to correspond to the number of outputchannels respectively. Then, the optical signal that propagates throughthe common optical waveguide 850 is incident on the corresponding lightconverging lens since its propagation direction is changed by theoptical deflector element on the output side, and then such opticalsignal is focused onto the corresponding optical output waveguide by thelight converging lens and then is output to the outside from the opticaloutput waveguide.

According to such configuration, in the optical switch 800, thepropagation direction of the input optical signal is changed in thecommon optical waveguide 850 by controlling the voltage applied to theoptical deflector elements on the incident side and the emissive side inthe common optical waveguide 850. Thus, the connection between any inputchannel and any output channel can be switched.

By the way, in the above optical switch 800, the light that propagatesthrough the waveguide layer 832 from the optical input waveguide 821 iscollimated by the lens curved surface 834 in the collimator portion 830.However, the light emitted from the optical input waveguide 821propagates through the waveguide layer 832 to spread radially.Therefore, in the waveguide layer 832, most of the incident lightpropagates through the area in which the light can be collimated by thelens curved surface 834. However, actually a part of the lightpropagates to the outside of this area.

In this manner, the light outside this area which can collimate suchlight propagates to the neighborhood of the edge portion of the lenscurved surface 834 or to the neighboring lens curved surface 834. Thus,there are some cases that the stray light is generated at theseportions. For example, the light that is propagated to the edge portionof the lens curved surface 834 is caused to spread in respectivedirections at this portion, and then the light that is propagated to theneighboring lens curved surface 834 is emitted from the lens curvedsurface 834 in the direction that is different from the direction todirect.

In particular, in the case of the optical switch 800 having a pluralityof input channels, the collimator portion 830 has a configuration suchthat the lens curves surfaces 234 of the two-dimensional lenses arealigned to correspond to respective input channels. Therefore, there wasa serious problem such that the crosstalk is generated due to the lightthat propagated to the neighboring lens curved surface 834.

Also, in the light converging lens in the light converging portion thatis provided to the common optical waveguide 850 on the output side, itis possible that a part of the light emitted from the optical deflectorelement on the preceding stage is not focussed onto the optical outputwaveguide on the output side. In this case, a part of the light isincident on the cladding area that surrounds the each optical outputwaveguide. In some cases, such light exerts a bad influence on theoptical signal that propagates through the optical output waveguide.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a couplingstructural body of optical parts capable of achieving a simplificationof manufacturing steps, improving a coupling efficiency at an opticalcoupling portion, and reducing a loss due to a reflection at aninterface between optical parts in the optical coupling portion, amethod of manufacturing the same, and an optical switch module.

It is another object of the present invention to provide atwo-dimensional lens array capable of preventing generation of acrosstalk between channels, and also improving a quality of thepropagated optical signal.

It is still another object of the present invention to provide anoptical switch capable of preventing the generation of the crosstalkbetween the channels, and also improving a quality of the propagatedoptical signal.

A coupling structural body of optical parts set forth in claim 1 of thisapplication is constructed by arranging a first optical waveguide havinga laminated structure of an underlying cladding layer with a refractiveindex nuj, a core layer with a refractive index ncj and an overlyingcladding layer with a refractive index noj, and a second opticalwaveguide having a laminated structure of an underlying cladding layerwith a refractive index nuk, a core layer with a refractive index nckand an overlying cladding layer with a refractive index nok so as tooppose end surfaces exposed with the overlying cladding layer to theunderlying cladding layer to each other, and then filling a fillingmedium with a refractive index ni(j,k) between the mutual end surfaces,whereby at least one end surface of both end surfaces is formed as atwo-dimensional lens and a light propagates from one optical waveguideto other optical waveguide through the filling medium.

According to the coupling structural body of optical parts described bythe present invention, both the first and second optical waveguides arearranged to oppose their end surfaces exposed with the overlyingcladding layer to the underlying cladding layer to each other, and aportion between the mutual end surfaces is filled with the fillingmedium with the refractive index ni(j,k).

In order to construct such structure, for example, the overlyingcladding layers, the core layers, and the underlying cladding layers arelaminated and then the overlying cladding layers to the underlyingcladding layers are etched continuously. Thus, the first and secondoptical waveguides are formed to oppose mutually their end surfacesexposed with the overlying cladding layers to the underlying claddinglayers. Then, a portion between the opposed end surfaces is filled withthe filling medium.

In this manner, since the polishing step set forth in the priorapplication (Patent Application No. 2001-332169) is not needed,simplification of the steps can be attained. Also, since filmthicknesses of the core layers, etc. are decided at the time of filmformation, control of the film thickness can be facilitated. Inaddition, a portion between the opposed end portions is filled with thefilling medium with the refractive index ni(j,k). Therefore, as shown inFIG. 8, if the refractive index ni(j,k) is selected appropriately, theloss can be reduced in contrast to the case where a portion between theend surfaces is filled with the air layer (ni(j,k)=1), and also themargin for the interval between the end surfaces can be delivered.

In the coupling structural body of optical parts set forth in claim 2 ofthis application, the refractive index ni(j,k) of the filling medium isselected such that, when the light propagates from one optical waveguideto other optical waveguide through the filling medium, a total loss of areflection loss and a coupling loss is reduced smaller than apredetermined value.

According to the present invention, as shown in FIG. 8, if therefractive index ni(j,k) (n2) of the filling medium is selectedappropriately, the loss can be reduced rather than the case where aportion between the opposing end surfaces is filled with the air layer(n2=1). Also, if the particular refractive index ni(j,k) (n2) isselected, the selectable range of the interval between the end surfacesto provide the loss that is smaller than the predetermined value can beexpanded. Thus, the margin for the interval between the end surfaces canbe delivered.

A method of manufacturing a coupling structural body of optical parts,set forth in claim 6 of this application comprises the steps oflaminating an underlying cladding layer with a refractive index nu, acore layer with a refractive index nc, and an overlying cladding layerwith a refractive index no on a substrate; etching continuously theunderlying cladding layer to the overlying cladding layer and thusforming a first optical waveguide and a second optical waveguide so asto oppose mutually those end surfaces exposed with the overlyingcladding layer to the underlying cladding layer; and filling a fillingmedium with a refractive index ni(j,k) between opposing end surfaces.

According to the method of manufacturing the coupling structural body ofoptical parts of the present invention, the first optical waveguide andthe second optical waveguide are formed so as to oppose mutually thoseend surfaces exposed with the overlying cladding layer to the underlyingcladding layer. Then, a portion between the opposing end surfaces isfilled with the filling medium.

Therefore, since the polishing step set forth in the prior applicationis not needed, simplification of the steps can be attained. Also, sincefilm thicknesses of the core layers, etc. are decided at the time offilm formation, the control of the film thickness can be facilitated.

An optical switch module set forth in claim 8 of this applicationcomprises a collimator portion for collimating a plurality of opticalsignals individually by two-dimensional lenses respectively; a pluralityof first optical deflector elements for switching individuallypropagation directions of the respective optical signals passed throughthe collimator portion by using an electrooptic effect; a common opticalwaveguide for propagating the optical signals passed through theplurality of first optical deflector elements respectively; a pluralityof second optical deflector elements for switching individually thepropagation directions of the respective optical signals passed throughthe common optical waveguide by using the electrooptic effect; and alight converging portion for converging individually the respectiveoptical signals passed through the plurality of second optical deflectorelements by the two-dimensional lenses; wherein at least any one of thecollimator portion and the light converging portion is provided with thecoupling structural body of optical parts set forth in any one of claim1 and claim 5.

According to the optical switch module of the present invention, sincethe coupling structural body of optical parts set forth in claim 1 or 2is provided, simplification of the manufacturing steps can be attained,and also the coupling efficiency can be improved. Thus, the loss causedby the reflection at interfaces of the optical coupling portion can bereduced.

In a coupling structural body of optical parts set forth in claim 10 ofthis application, a first optical waveguide having at least a core layerwith a refractive index ncj and a second optical waveguide having atleast a core layer with a refractive index nck are arranged to opposeend surfaces to each other, any one of the end surfaces of the firstoptical waveguide and the second optical waveguide is formed by etching,and the end surface formed by the etching is covered with a coatingmedium having a refractive index nij or nik that is equal to arefractive index ncj or nck of the core layer exposed from the endsurface.

According to the coupling structural body of optical parts of thepresent invention, the end surface formed by the etching is covered withthe coating medium having the refractive index nij or nik that is equalto the refractive index ncj or nck of the core layer exposed from theend surface.

Since the refractive index nij or nik of the coating medium is equal tothe refractive index ncj or nck of the core layer exposed from the endsurface, such coating medium can be practically regarded as the corelayer with respect to the propagation of the light. Therefore, even ifthe unevenness is generated by the etching on the end surface at theopposing portions of the first or second optical waveguide, thesubstantially smooth end surface of the optical waveguide can beobtained by uniformizing the unevenness on the end surface by means ofthe coating medium. As a result, the light which propagates through theoptical waveguide can be prevented from the scattering at the endsurface, and thus the loss due to the reflection and the coupling losscan be reduced.

In the coupling structural body of optical parts set forth in claim 12of this application, the end surface of at least any one of the firstand second optical waveguides constitutes a two-dimensional convex lens.In the coupling structural body of optical parts set forth in claim 13of this application, a filling medium having a refractive index ni(j,k)which is lower than the refractive index ncj or nck, as well as aportion between opposing end surfaces is filled with the coating mediumthat coats the end surface.

According to the coupling structural body of optical parts of thepresent invention, the area next to the two-dimensional convex lenseswhose end surfaces are made smooth by the coating medium is filled withthe filling medium with the refractive index ni(j,k), which is lowerthan the refractive indexes of the core layers. Thus the loss due to thereflection can be reduced and also the light that is transmitted throughthe two-dimensional lenses can be collimated. Therefore, the propagationloss of the light can be reduced.

In the coupling structural body of optical parts set forth in claim 14of this application, the end surface of at least any one of the firstand second optical waveguides constitutes a two-dimensional concavelens. In the coupling structural body of optical parts set forth inclaim 15 of this application, a filling medium having a refractive indexni(j,k) which is higher than the refractive index ncj or nck, as well asa portion between opposing end surfaces is filled with the coatingmedium that coats the end surface.

According to the coupling structural body of optical parts of thepresent invention, the area next to the two-dimensional convex lenseswhose end surfaces are made smooth by the coating medium is filled withthe filling medium with the refractive index ni(j,k) which is lower thanthe refractive indexes of the core layers. Thus the loss due to thereflection can be reduced and also the light that is transmitted throughthe two-dimensional lenses can be collimated. Therefore, the propagationloss of the light can be reduced.

An optical switch module set forth in claim 16 of this applicationcomprises a collimator portion for collimating a plurality of opticalsignals individually by two-dimensional lenses respectively; a pluralityof first optical deflector elements for switching individuallypropagation directions of the respective optical signals passed throughthe collimator portion by using an electrooptic effect; a common opticalwaveguide for propagating the respective optical signals that are passedthrough the plurality of first optical deflector elements respectively;a plurality of second optical deflector elements for switchingindividually the propagation directions of the respective opticalsignals passed through the common optical waveguide by using theelectrooptic effect; and a light converging portion for convergingindividually the respective optical signals passed through the pluralityof second optical deflector elements by the two-dimensional lenses;wherein any one of the collimator portion and the light convergingportion is provided with the coupling structural body of optical partsset forth in any one of claim 10 and claim 15.

According to the optical switch module of the present invention, sincethe coupling structural body of optical parts set forth in any one ofclaims 10 to 15 is provided, the propagation loss of light in theoptical coupling portion can be reduced.

In order to overcome the above another problem, according to the presentinvention, as shown in FIG. 21, there is provided a two-dimensional lensarray which comprises a slab optical waveguide having anincident/emissive end surface into/from which a plurality of opticalsignals are input/output respectively; and a plurality of lens curvedsurf aces formed at a boundary surface between the slab opticalwaveguide and another medium with a different refractive index torespond to the optical signals respectively; wherein a light absorbingbody is provided on both sides of propagation areas of each opticalsignal between the incident/emissive end surface and each lens curvedsurface respectively.

In such two-dimensional lens array, for example, if the optical signalpropagates through the slab optical waveguide to the lens curved surface734, the light absorbing body 735 is provided in the slab opticalwaveguide on both sides of the propagation area of the optical signal,and therefore the extra light that is not precisely incident on the lenscurved surface 734 and the scattered light from the end portion of thelens curved surface 734, etc. can be absorbed by such light absorbingbody 735. Also, if the optical signal is incident on the slab opticalwaveguide from the lens curved surface 734, the extra light that passedthrough the lens curved surface 734 and then propagates through theoutside of the predetermined area of the emissive end can be absorbed bythe light absorbing body 735.

Also, according to the present invention, there is provided an opticalswitch for switching a propagation path of an optical signal, whichcomprises a plurality of optical input waveguides for receiving opticalsignals from an outside; a plurality of optical output waveguides foroutputting the optical signals to the outside; a plurality of collimatorlenses for collimating the optical signals, which passed through theoptical input waveguides, individually; first light absorbing bodiesarranged on both sides of propagation areas of the optical signals inthe collimator lenses corresponding to the respective optical inputwaveguides; a plurality of input-side optical deflector elements forswitching propagation directions of the optical signals, which passedthrough the respective collimator lenses, individually; a common opticalwaveguide through which the optical signals that passed through theinput-side optical deflector elements propagate commonly; a plurality ofoutput-side optical deflector elements for switching the propagationdirections of the optical signals, which passed through the commonoptical waveguide, individually; a plurality of light converging lensesfor focusing the optical signals, which passed through the output-sideoptical deflector elements, onto the optical output waveguidesindividually; and second light absorbing bodies arranged on both sidesof the propagation areas of the optical signals that propagate from thelight converging lenses to the optical output waveguides.

In such optical switch, since the first light absorbing body is providedon both sides of the propagation area of the optical signal from theoptical input waveguide to the corresponding collimator lens, the extralight that is not precisely incident on the collimator lens and thescattered light from the end portion of the lens curved surface of thecollimator lens, etc. can be absorbed by such first light absorbingbody. Also, since the second light absorbing body is provided on bothsides of the propagation area of the optical signal from the lightconverging lens to the corresponding optical output waveguide, the extralight that is not precisely incident on the optical output waveguide canbe absorbed by such second light absorbing body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan view showing an example of a configuration of a partof the optical switch using the optical deflector element in the priorart, and FIG. 1B is a sectional view showing the same;

FIG. 2 is a schematic plan view showing an optical signal switchingdevice using an optical switch module according to a first embodiment ofthe present invention;

FIG. 3 is a schematic plan view showing a configuration of the opticalswitch module according to the first embodiment of the presentinvention;

FIG. 4A is a perspective view showing coupling portions between atwo-dimensional convex lens and an optical waveguide as the firstembodiment, FIG. 4B is a perspective view showing an optical waveguideand a two-dimensional concave lens as the first embodiment, and FIG. 4Cis a sectional view showing a behavior of light propagation in thecoupling portions in FIG. 4A and FIG. 4B;

FIG. 5A is a perspective view showing a coupling portion between atwo-dimensional convex lens and an optical waveguide in a comparativeexample, and FIG. 5B is a sectional view showing a behavior of lightpropagation in the coupling portion;

FIG. 6 is a graph showing calculated results of a reflection loss withrespect to a refractive index of a filling medium in the opticalcoupling portion as the first embodiment;

FIG. 7 is a graph showing calculated results of a coupling loss withrespect to the refractive index of the filling medium while using aninterval between end surfaces as a parameter, in the optical couplingportion as the first embodiment;

FIG. 8 is a graph showing examined results of a total loss that isobtained by adding both the reflection loss and the coupling loss withrespect to the refractive index of the filling medium while using theinterval between the end surfaces as the parameter, in the opticalcoupling portion as the first embodiment;

FIGS. 9A to 9C are sectional views, as lower views, showing a method offorming coupling portions between two-dimensional convex lenses and theoptical waveguides, which are similar to FIG. 4A, according to a secondembodiment of the present invention, and plan views, as upper views,showing the same;

FIGS. 10A to 10C are sectional views, as lower views, showing a methodof forming coupling portions between two-dimensional concave lenses andthe optical waveguides, which are similar to FIG. 4B, according to thesecond embodiment of the present invention, and plan views, as upperviews, showing the same;

FIGS. 11A to 11D are views showing a method of forming coupling portionsbetween two-dimensional convex lenses and the optical waveguidesaccording to a third embodiment of the present invention, wherein theirupper views are plan views and their lower views are sectional views;

FIGS. 12A to 12D are views showing a method of forming coupling portionsbetween two-dimensional concave lenses and the optical waveguidesaccording to the third embodiment of the present invention, whereintheir upper views are plan views and their lower views are sectionalviews;

FIG. 13 is a plan view, as an upper view, showing a coupling portionbetween two-dimensional lenses and the optical waveguides according to afourth embodiment of the present invention, and a sectional view, as alower view, taken along a I—I line in the upper view;

FIG. 14 is a plan view, as an upper view, showing another couplingportion between two-dimensional lens and the optical waveguide accordingto the fourth embodiment of the present invention, and a sectional view,as a lower view, taken along a II—II line in the upper view;

FIG. 15A is a plan view showing a coupling portion betweentwo-dimensional convex lenses to explain a fifth embodiment of thepresent invention, and FIG. 15B is a sectional view taken along aIII—III line in FIG. 15A;

FIG. 16 is a sectional view showing a configuration of a couplingstructural body of optical parts according to the fifth embodiment ofthe present invention;

FIG. 17A is an enlarged plan view showing a configuration of acollimator portion or a light converging portion of an optical switchmodule according to a sixth embodiment of the present invention, andFIG. 17B is a sectional view taken along a IV—IV line in FIG. 17A;

FIG. 18A is a plan view showing a configuration of a coupling structuralbody of optical parts having a collimator portion of the optical switchmodule according to a seventh embodiment of the present invention, andFIG. 18B is a sectional view taken along a V—V line in FIG. 18A;

FIG. 19 is a plan view showing a configuration of an optical switchmodule according to an eighth embodiment of the present invention;

FIG. 20A is a plan view showing a configuration of a coupling structuralbody of an incident-side channel waveguide portion and a collimatorportion of the optical switch module according to the eighth embodimentof the present invention, and FIG. 20B is a sectional view taken along aVI—VI line in FIG. 20A;

FIG. 21 is a plan view showing a configuration of a collimator portionand its periphery of a two-dimensional lens array according to a ninthembodiment of the present invention;

FIG. 22 is a plan view showing an example of a configuration of anoptical switch module having the two-dimensional lens array according tothe ninth embodiment of the present invention;

FIGS. 23A and 23B are sectional views showing the configurations of thecollimator portion and its periphery respectively;

FIG. 24 is a plan view showing configurations of a light convergingportion of its periphery of the two-dimensional lens array according tothe ninth embodiment of the present invention; and

FIGS. 25A, 25B, and 25C are sectional views showing a method ofmanufacturing the optical switch module respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be explained with reference tothe drawings hereinafter.

First Embodiment

FIG. 2 is a schematic plan view showing an optical signal switchingdevice using an optical switch module according to a first embodiment ofthe present invention. This optical signal switching device receives at40 Gb/s and 64-system WDM signals in which the optical signalscorresponding to 64 wavelengths are multiplexed and then switchestransmission destinations of these optical signals.

This optical signal switching device is constructed by 64 AWG opticaldemultiplexers 101 aligned in the vertical direction, an optical switchmodule group 100 having a 3-stage configuration, 64 optical multiplexers103, and 64 optical amplifiers (EDFA: Erbium Doped Fiber Amplifier) 104.The optical switch module group 100 comprises a set of optical switchmodule group which is constructed by arranging 64 64×64-channel opticalswitch modules 102 in the direction that is perpendicular to thesubstrate, and then the second-stage optical switch module group isrotated with respect to first and third-stage optical switch modulegroups by 90.

Also, optical connectors 105 connect the optical demultiplexer 101 withthe first-stage optical switch module group, and the third-stage opticalswitch module group with the optical multiplexer 103 respectively.Optical connectors 106 connect the first-stage optical switch modulegroup with the second-stage optical switch module group, and thesecond-stage optical switch module group with the third-stage opticalswitch module group respectively. The optical connectors 105, 106consist of the substrate and a large number of micro lenses that passthe light in the thickness direction of this substrate.

Lenses of these optical connectors 105, 106 converge the light outputfrom the optical device at the preceding stage to transmit such light tothe optical device at the succeeding stage, and thus are useful forreduction in a propagation loss.

In this optical signal switching device, the multiplexed optical signalis separated into individual optical signals by the opticaldemultiplexer 101. Then, propagation destinations of respective opticalsignals are switched by the optical switch module group 100. Here, threesets of optical switch module groups are constructed by combining 6464×64-channel optical switch modules 102 respectively such thatthree-stage configuration (cascade connection) is constructed byrotating each of three sets of optical switch module groups by 90. Thus,the optical signal that is input into any input port can be output toany output port of 4096 output ports. The optical signals whosetransmission destinations are switched by the optical signal switchingdevice are multiplexed by the optical multiplexer 103 every destination,then amplified by the optical amplifier 104, and then output.

In the optical signal switching device shown in FIG. 2, each of thefirst, second, and third optical switch module groups is constructed byarranging 64 64×64-channel optical switch modules 102 respectively.However, the first and third optical switch module groups may beconstructed by arranging 128 optical switch modules 102 in 2 columnsalong the width direction and in 64 columns along the height direction,while the second optical switch module group may be constructed by 12864×64-channel optical switch modules 102 being arranged in the directionthat is rotated by 90 with respect to the optical switch modules 102 inthe first and third optical switch module groups.

In this case, the description is performed with respect to the case ofcontrolling the deflection angle of the optical signal by changing thevoltage applied to control electrodes in the prism pairs. But thedeflection angle of the optical signal may be controlled by changing thenumber of the prism pairs, to which the control voltage is applied,while keeping the control voltage at a constant level.

FIG. 3 is a schematic plan view showing a configuration of the opticalswitch module 102 according to the first embodiment of the presentinvention.

This optical switch module 102 consists of an incident-side opticalwaveguide portion 201, a collimator portion 202, an incident-sideoptical deflector element portion (first optical deflector element) 203,a common optical waveguide portion 204, an emissive-side opticaldeflector element portion (second optical deflector element) 205, alight converging portion 206, and an emissive-side optical waveguideportion 207. The incident-side optical waveguide portion 201, thecollimator portion 202, the incident-side optical deflector elementportion 203, the common optical waveguide portion 204, the emissive-sideoptical deflector element portion 205, the light converging portion 206,and the emissive-side optical waveguide portion 207 are formed on thesubstrate. Then, a coupling structural body of optical parts is providedto at least to any one of the collimator portion 202 and the lightconverging portion 206.

The incident-side optical waveguide portion 201 consists of a pluralityof core layers 201 b as the main optical waveguides, and cladding layersfor covering these core layers 201 b to confine the light within thecore layers 201 b due to difference in their refractive indexes. Likethis, the emissive-side optical waveguide portion 207 consists of aplurality of core layers 207 b as the main optical waveguides, andcladding layers for covering these core layers 207 b to confine thelight within the core layers 207 b due to difference in their refractiveindexes.

In the present embodiment, assume that the number of the opticalwaveguides (core layers) 201 b in the incident-side optical waveguideportion 201 is set equal to the number of the optical waveguides (corelayers) 207 b in the emissive-side optical waveguide portion 207.However, the present invention is not limited to this. The number of theincident-side optical waveguides may be set differently from the numberof the emissive-side optical waveguides.

The collimator portion 202 consists of n pieces of collimator lenses(core layers) 202 b. The collimator lenses 202 b are arranged atpositions that are slightly remote from end portions of the opticalwaveguides 201 b respectively. The light that is emitted from theoptical waveguide 201 b spreads radially and then becomes a parallellight by the collimator lens 202 b.

The incident-side optical deflector element portion 203 is provided withn pieces of optical deflector elements 203 p each having the opticalwaveguide through which the optical signal propagates. The opticaldeflector elements 203 p are arranged at positions that are slightlyremote from the collimator lenses 202 b in the optical-axis directionrespectively. The optical deflector elements 203 p deflect thepropagation direction of the optical signal by utilizing the Pockelseffect (electrooptic effect).

The common optical waveguide portion 204 has the slab waveguides. Thecommon optical waveguide portion 204 transmits the light, which passedthrough the incident-side optical deflector element portion 203, to theemissive-side optical deflector element portion 205. A plurality ofoptical signals pass simultaneously through the slab waveguides. Sincethese optical signals go straight on in the slab waveguides in thedetermined direction, such optical signals can be transmitted withoutinterference with other optical signals.

The emissive-side optical deflector element portion 205 is provided withn pieces of optical deflector elements 205 p each having the opticalwaveguide through which the optical signal propagates. These opticaldeflector elements 205 p deflect the lights, which come up to theoptical deflector elements 205 p through the common optical waveguideportion 204, in the direction that is parallel with the opticalwaveguide. The optical deflector elements 205 p have basically the samestructure as the optical deflector elements 203 p in the incident-sideoptical deflector element portion 203.

The light converging portion 206 have n pieces of light converginglenses 206 b that are formed by patterning the core layer. These lightconverging lenses 206 b have a function of converging the lights, whichpassed through the optical deflector elements 205 p, to lead such lightsto the optical waveguides (core layers) 207 b in the emissive-sideoptical waveguide portion 207.

The description is performed partially with respect to the emissive-sideoptical waveguide portion 207 in connection with the incident-sideoptical waveguide portion 201. In addition, like the arrangement of theoptical waveguides 201 b and the collimator lenses 202 b in theincident-side optical waveguide portion 201, the light converging lenses206 b are arranged at positions that are slightly remote from endportions of the optical waveguides 207 b in the emissive-side opticalwaveguide portion 207 respectively. Then, the parallel lights areconverged into the optical waveguides 207 b by the light converginglenses 206 b.

Next, the description will be performed with respect to the couplingstructural bodies of the optical parts such as the optical propagationsystem, the image forming system, the optical deflector system, etc.with reference to FIGS. 4A to 4C hereunder.

FIG. 4A is a perspective view showing coupling portions between atwo-dimensional convex lens 601 and an optical waveguide 602 as thefirst embodiment, FIG. 4B is a perspective view showing an opticalwaveguide 611 and a two-dimensional concave lens 612 as the firstembodiment, and FIG. 4C is a sectional view showing a behavior of lightpropagation in the coupling portions in FIG. 4A and FIG. 4B.

Now, the description will be performed hereunder with respect to thecase where the light propagates from the left to the right. But the sameis true of the case where the light propagates oppositely. Therefore,the optical waveguides 602, 611 constitute the incident-side opticaldeflector element portion 203 and the emissive-side optical deflectorelement portion 205, for example. Otherwise, in some cases such opticalwaveguides 602, 611 constitute the common optical waveguide portion 204that is directly coupled to two-dimensional lenses 202, 206 by omittingthe incident-side optical deflector element portion 203 and theemissive-side optical deflector element portion 205.

In FIG. 4A, a feature of the coupling portion between thetwo-dimensional convex lens 601 and the optical waveguide 602 will begiven as follows. The first optical waveguide 601, which is formed bylaminating an underlying cladding layer 601 a with a refractive indexnu1 (nuj), a core layer 601 b with a refractive index n1 (nc1(ncj)), andan overlying cladding layer 601 c with a refractive index no1 (noj), andthe second optical waveguide 602, which is formed by laminating anunderlying cladding layer 602 a with a refractive index nu2 (nuk), acore layer 602 b with a refractive index n2 (nc2(nck)), and an overlyingcladding layer 602 c with a refractive index no2 (nok), are arranged tooppose their end surfaces to each other. The end surfaces are formed byetching successively the overlying cladding layer to the underlyingcladding layer. The end surface of the first optical waveguide 601constitutes two-dimensional convex lens. A portion between opposing endsurfaces is filled with filling medium 603 with a refractive index n2(ni12(ni(j,k))). The light propagates from the first optical waveguide601 to the second optical waveguide 602 via the filling medium 603. Therefractive index n2 of the filling medium 603 is selected such that,when the light propagates through this coupling portion, a total loss ofa reflection loss and a coupling loss is reduced smaller than apredetermined value.

From a viewpoint of reducing the reflection loss and the coupling loss,a value that is higher or lower than the refractive index n1 may beemployed as the refractive index n2. It is preferable that, if the abovecoupling structural body is applied to the optical switch module, thevalue of the refractive index n2 should be set lower than the refractiveindex n1 to collimate the light by the two-dimensional concave lens 601in the collimator portion and to converge the light in the lightconverging portion. Hence, as shown in FIG. 4A, the vertical spread ofthe propagated light can be suppressed and the above coupling structuralbody contributes to the reduction in loss.

In FIG. 4B, the coupling portion between the optical waveguide 611 andthe two-dimensional concave lens 612 has the same structure as thatshown in FIG. 4A except a planar shape of the two-dimensional concavelens 612.

In other words, the first optical waveguide 611, which is formed bylaminating an underlying cladding layer 611 a with a refractive indexnu1 (nuj), a core layer 611 b with a refractive index n1 (nc1(ncj)), andan overlying cladding layer 611 c with a refractive index no1 (noj), andthe second optical waveguide 612, which is formed by laminating anunderlying cladding layer 612 a with a refractive index nu2 (nuk), acore layer 612 b with a refractive index n2 (nc2(nck)), and an overlyingcladding layer 612 c with a refractive index no2 (nok), are arranged tooppose their end surfaces to each other. The overlying cladding layers611 c, 612 c to the underlying cladding layers 611 a, 612 a are exposedfrom both end surfaces of the opposing portions. The end surface of thesecond optical waveguide (core layer) 612 b constitutes thetwo-dimensional concave lens.

Then, a refractive index n2 (ni12(ni(j,k))) of a filling medium 613between the opposing end surfaces is selected such that, when the lightpropagates through this coupling portion, the total loss of thereflection loss and the coupling loss is reduced smaller than apredetermined value.

In this case, from a viewpoint of reducing the reflection loss and thecoupling loss, the value that is higher or lower than the refractiveindex n1 may also be employed as the refractive index n2. If the abovecoupling structural body is applied to the optical switch module,preferably the value of the refractive index n2 should be set higherthan the refractive index n1 to collimate the light by thetwo-dimensional concave lens 612 in the collimator portion and toconverge the light in the light converging portion. Hence, as shown inFIG. 4C, it can suppress the vertical spread of the propagated light andcontributes to the reduction in loss.

Examined results of the reflection loss and the coupling loss in thecoupling structural body of the optical parts according to the firstembodiment will be explained with reference to FIG. 6, FIG. 7, and FIG.8 hereunder.

For comparison, the reflection loss and the coupling loss in thecoupling structural body of the optical parts in FIGS. 5A and 5B weresimilarly examined. FIG. 5A is a perspective view showing a couplingportion between a two-dimensional convex lens 621 and an opticalwaveguide 622, and FIG. 5B is a sectional view showing a behavior oflight propagation in the coupling portion. In this comparative example,as shown in FIG. 5A, the concave portion in the opposing portion is notfilled with the filling medium whose refractive index is larger than 1but smaller than the refractive index of the core layer, and it isfilled with the air which refractive index is 1.

FIG. 6 is a graph showing calculated results of the reflection loss.FIG. 7 is a graph showing calculated results of the coupling loss. FIG.8 is a graph showing examined results of the total loss that is obtainedby adding both the reflection loss and the coupling loss. These examinedresults were derived by the simulation executed based on the model shownin FIG. 3, and show the results that are obtained by summing both theincident side and the emissive side. In the model shown in FIG. 3, forexample, the coupling portion between the collimator portion 202 and theoptical deflector element portion 203 on the incident side and thecoupling portion between the optical deflector element portion 205 andthe light converging portion 206 on the emissive side are assumed. Here,assume that the core layer of the two-dimensional lens and the corelayer of the optical deflector element have the same refractive index n1(=1.5702) and also the filling media with which the concave portions inrespective coupling portions are filled have the same refractive indexn2.

FIG. 6 shows a relationship between the refractive index n2 of themedium with which the concave portion between the opposing portions inthe coupling portion is filled, and the reflection loss. As shown in anupper view of FIG. 6, the calculation is executed under the assumptionthat a reflection is generated at a boundary surface between the mediawith different refractive indexes. An ordinate of FIG. 6 denotes thereflection loss (dB) in a linear scale, and an abscissa thereof denotesthe refractive index n2 of the medium, with which the concave portionbetween the opposing portions in the coupling portion is filled, in alinear scale.

As shown in FIG. 6, the reflection loss was smallest at a point wherethe refractive index n2 is equal to the refractive index n1. If therefractive index n2 is 1 (in the case of the comparative example), i.e.,if in the concave portion between the opposing portions is filled withthe air, such reflection loss was about −0.8 dB. If the refractive indexn2 is 3, such reflection loss was about −1.8 dB.

FIG. 7 shows a relationship between the refractive index n2 of themedium, with which the concave portion between the opposing portions isfilled, and the coupling loss, while using an interval (μm) between theopposing portions as a parameter. An ordinate of FIG. 7 denotes thecoupling loss (dB) in a linear scale, and an abscissa thereof denotesthe refractive index n2 of the medium, with which the concave portionbetween the opposing portions is filled, in a linear scale.

As shown in FIG. 7, the coupling loss is increased larger as theinterval between the opposing portions is widened, while the couplingloss is increased larger as the refractive index n2 is reduced lower. Ifthe refractive index n2 is 1 (in the case of the comparative example)and the interval is 10 μm, the coupling loss was seldom generated, i.e.,became about 0 dB. If the interval is 100 μm, the coupling loss wasabout −3.7 dB. Also, if the refractive index n2 is 1.57 and the intervalis 10 μm, the coupling loss was seldom generated, i.e., became about 0dB. If the interval is 100 μm, the coupling loss was about −2.4 dB. Inaddition, if the refractive index n2 is 3 and the interval is 10 μm, thecoupling loss was seldom generated, i.e., became about 0 dB. If theinterval is 100 μm, the coupling loss was about −0.7 dB.

FIG. 8 shows a relationship between the refractive index n2 of themedium, with which the concave portion between the opposing portions isfilled, and the total loss derived by summing the reflection loss andthe coupling loss, while using the interval (μm) between the opposingportions as the parameter. An ordinate of FIG. 8 denotes the total loss(dB) in a linear scale, and an abscissa thereof denotes the refractiveindex n2 of the medium, with which the concave portion between theopposing portions is filled, in a linear scale.

As shown in FIG. 8, like the change in the reflection loss with respectto the refractive index n2, the total loss was smallest at a point wherethe refractive index n2 is equal to the refractive index n1 or in theneighborhood that is higher than the refractive index n1. The total lossis increased as the interval is widened longer. If the refractive indexn2 is 1 (in the case of the comparative example) and the interval is 10μm, such total loss was about −1 dB. If the interval is 100 μm, thetotal loss was smaller than about −4 dB. Also, if the refractive indexn2 is 1.57 and the interval is 10 μm, the total loss was seldomgenerated and was about 0 dB. If the interval is 100 μm, the total losswas about −2.4 dB. In addition, if the refractive index n2 is 3 and theinterval is 10 μm, the total loss was about −1.9 dB. If the interval is100 μm, the total loss was about −2.5 dB. It is appreciated that, inorder to suppress the total loss within about −0.5 dB, the interval mustbe set to 40 μm or less. If the interval is 40 μm, the selectable rangeof the refractive index n2 was about 1.6 to 1.8. If the interval isnarrower than this interval, the selectable range of the refractiveindex n2 was expanded. Also, if the interval is 10 μm, the selectablerange of the refractive index n2 was about 1.1 to 2.2.

As described above, according to the first embodiment of the presentinvention, both the first and second optical waveguides 601 or 611 and602 or 612 are arranged to oppose their end surfaces from which theoverlying cladding layers 601 c, 611 c, 602 c, 612 c to the underlyingcladding layers 601 a, 611 a, 602 a, 612 a are exposed, and a portionbetween the mutual end surfaces is filled with the filling medium 603 or613 with the refractive index n2.

Although explained in detail in a second embodiment, in order toconstruct such structure, for example, the overlying cladding layers 601c, 611 c, 602 c, 612 c to the underlying cladding layers 601 a, 611 a,602 a, 612 a, which are laminated continuously, are etched continuously.Thus, the first and second optical waveguides 601 or 611 and 602 or 612are formed to oppose mutually their end surfaces from which theoverlying cladding layers 601 c, 611 c, 602 c, 612 c to the underlyingcladding layers 601 a, 611 a, 602 a, 612 a are exposed. Then, a portionbetween the opposed end surfaces is filled with the filling medium 603or 613.

In this case, since the polishing step set forth in the priorapplication (Patent Application No. 2001-332169) is not needed,simplification of the steps can be attained. Also, since filmthicknesses of the core layers 601 b, 611 b, 602 b, 612 b, etc. aredecided at the time of film formation, control of the film thickness canbe facilitated.

Also, a portion between the opposed end portions is filled with thefilling medium 603 or 613 with the refractive index n2. Therefore, asshown in FIG. 8, if the refractive index n2 is selected appropriately,the loss can be reduced in contrast to the case where a portion betweenthe end surfaces is filled with the air layer (n2=1), and also themargin for the interval between the end surfaces can be delivered.

In this case, in the first embodiment, materials with the samerefractive index n1 are employed as the core layers 601 b, 611 b, 602 b,612 b of the first and second optical waveguides 601 or 611 and 602 or612. But the core layers with the different refractive indexes (nc1,nc2)may be employed. In this case, the refractive index ni12 of the fillingmedium 603 or 613 is set such that the total loss in the opticalcoupling portion can be reduced lower than the predetermined value. Inaddition, in the application of the optical switch module, it ispreferable that nc1, nc2>ni12>1 should be satisfied in the case oftwo-dimensional convex lens. As such material, the fluororesin whoserefractive index is lower than that of the quartz is employed. Also, itis preferable that nc1, nc2<ni12 should be satisfied in the case oftwo-dimensional concave lens. As such material, the epoxy resin whoserefractive index is higher than that of the quartz, or the like isemployed.

Second Embodiment

Next, a method of forming coupling portions between two-dimensionalconvex lenses and the optical waveguides, which are similar to FIG. 4A,according to a second embodiment of the present invention will beexplained with reference to FIGS. 9A to 9C hereinafter.

In each of FIGS. 9A to 9C, an upper view is a plan view and a lower viewis a sectional view.

First, as shown in FIG. 9A, an SiO₂ film 21 with a refractive index 1.44as an underlying cladding layer, an SiO₂ film 22 with a refractive index1.45 as a core layer, and an SiO₂ film 23 with a refractive index 1.44as an overlying cladding layer are deposited sequentially on a quartzsubstrate 20 by the CVD (Chemical Vapor Deposition) method. Adjustmentof the refractive index is executed by controlling the film formingconditions.

Then, as shown in FIG. 9B, the two-dimensional lens 601 having a convexend surface and the optical waveguide 602 having the flat end surfaceare formed at a distance by the reactive ion etching while using aphotoresist mask (not shown). Thus, the convex end surface of thetwo-dimensional lens 601 and the flat end surface of the opticalwaveguide 602 are opposed to each other at an interval. The underlyingcladding layer 601 a, the core layer 601 b, and the overlying claddinglayer 601 c are exposed from the end surface of the two-dimensional lens601. The underlying cladding layer 602 a, the core layer 602 b, and theoverlying cladding layer 602 c are exposed from the end surface of theoptical waveguide 602.

Then, as shown in FIG. 9C, a portion between the opposing portions isfilled with the fluororesin (filling medium) 603 with the refractiveindex n2 (ni12) that is selected in the range, in which the total lossof the reflection loss and the coupling loss can be reduced smaller thanthe predetermined value when the light propagates from thetwo-dimensional lens 601 to the optical waveguide 602 through theopposing portions. In this case, it is preferable that, if the abovecoupling structural body is applied to the optical switch module, thevalue of the refractive index n2 (ni12) should be set lower than therefractive index n1 to collimate the light by the two-dimensionalconcave lens 601 in the collimator portion and to converge the light inthe light converging portion.

Thus, the coupling structural body of the optical parts, one of which isthe two-dimensional convex lens, is completed.

Next, a method of forming coupling portions between the opticalwaveguides and two-dimensional concave lenses, which are similar to FIG.4B, according to a second embodiment of the present invention will beexplained with reference to FIGS. 10A to 10C hereinafter. In each ofFIGS. 10A to 10C, an upper view is a plan view and a lower view is asectional view.

As shown in FIGS. 10A to 10C, the optical waveguide 611 and thetwo-dimensional concave lens 612 are formed at a distance. Such partscan be formed in the same manner as that in FIGS. 9A to 9C. Thus, astructure in which the optical waveguide 611 and the two-dimensionalconcave lens 612 are arranged to oppose their end surfaces mutually isobtained. The underlying cladding layer 611 a, the core layer 611 b, andthe overlying cladding layer 611 c are exposed from the end surface ofthe optical waveguide 611. The underlying cladding layer 612 a, the corelayer 612 b, and the overlying cladding layer 612 c are exposed from theend surface of the two-dimensional concave lens 612.

Then, as shown in FIG. 10C, a portion between the opposing portions isfilled with the epoxy resin (filling medium) 613 with the refractiveindex n2 (ni12 (ni(j,k))) that is selected in the range, in which thetotal loss of the reflection loss and the coupling loss can be reducedsmaller than the predetermined value when the light propagates from theoptical waveguide 611 to the two-dimensional concave lens 612 throughthe opposing portions. In this case, it is preferable that, in theapplication of the optical switch module, normally the value of therefractive index n2 (ni12) should be set higher than the refractiveindex n1 of the core layer 611 b, 612 b to collimate the light by thetwo-dimensional concave lens 612 in the collimator portion and toconverge the light in the light converging portion.

Thus, the coupling structural body of the optical parts, one of which isthe two-dimensional concave lens 612, is completed.

As described above, according to the second embodiment, thetwo-dimensional concave lens 601 or 612 and the optical waveguide 602 or611, whose end surfaces are opposed to put the opposing portionstherebetween, are formed by etching successively the laminated structureas the optical waveguide from the overlying cladding layer 23 to theunderlying cladding layer 21. Then, a portion between the opposingportions is filled with the resin 603, 613 with the refractive index n2(ni12) that is selected in the range, in which the total loss of thereflection loss and the coupling loss can be reduced smaller than thepredetermined value when the light propagates through the couplingportion.

As a result, simplification of the manufacturing steps can be attained,and the coupling efficiency can be improved. Thus, the loss caused bythe reflection at interfaces of the optical coupling portion can bereduced.

Third Embodiment

Next, a third embodiment of the present invention will be explained withreference to FIGS. 11A to 11D and FIGS. 12A to 12D hereunder.

An upper view of FIG. 11D is a plan view showing coupling portionsbetween two-dimensional convex lenses and the optical waveguidesaccording to the third embodiment, and a lower view of FIG. 11D is asectional view showing the same.

In the third embodiment, a difference from the structures of thecoupling portions in the first and second embodiments resides in thatrespective end surfaces of the two-dimensional lens 601 and the opticalwaveguide 602 in the optical coupling portion are covered with films(coating mediums) 601 d, 602 d made of material having the intermediaterefractive index ni1 (nij) or ni2 (nik) between the refractive index n1(nc1(ncj), nc2(nck)) of the core layers 601 b, 602 b in thetwo-dimensional lens 601 and the optical waveguide 602 and therefractive index n2 (ni12(ni(j,k))) of the medium 603 with which aportion between the opposing portions is filled, respectively. It isdesired that the films 601 d, 602 d for covering the end surfaces shouldbe formed sufficiently thin rather than the interval between theopposing portions. Preferably, the thickness should be set smaller thanseveral μm.

As shown in FIGS. 11A and 11B, in the manufacturing method, thetwo-dimensional convex lens 601 and the optical waveguide 602 are formedto put the opposing portions therebetween. In this case, the same stepsas those in FIGS. 9A and 9B are applied. Thus, the structure in whichthe two-dimensional lens 601 and the optical waveguide 602 are arrangedto oppose their end surfaces mutually is obtained. The underlyingcladding layer 601 a, the core layer 601 b, and the overlying claddinglayer 601 c are exposed from the end surface of the two-dimensional lens601. The underlying cladding layer 602 a, the core layer 602 b, and theoverlying cladding layer 602 c are exposed from the end surface of theoptical waveguide 602.

Then, as shown in FIG. 11C, the resin having the intermediate refractiveindex n3 (ni1(nij), ni2(nik)) between the refractive index n2(ni12(ni(j,k))) of the resin 603, with which a portion between theopposing portions is filled later, and the refractive index n1(nc1(ncj), nc2(nck)) of the core layers 601 b, 602 b is selected. Then,the thin resin film (coating medium) 601 d, 602 d for covering the endsurface of the two-dimensional lens 601 and the end surface of theoptical waveguide 602 respectively are formed by coating the resin byvirtue of the coating method.

Then, as shown in FIG. 11D, a portion between the end surface of thetwo-dimensional lens 601 and the end surface of the optical waveguide602, which are covered with the thin resin films 601 d, 602 d, is filledwith the resin (filling medium) 603 with the refractive index n2 that islower than the refractive index n3 of the thin resin films 601 d, 602 d,respectively. Thus, the coupling structural body of the optical parts,one of which is the two-dimensional convex lens, is completed.

Next, coupling portions between two-dimensional concave lenses and theoptical waveguides and a method of forming the same according to thethird embodiment will be explained with reference to FIGS. 12A to 12Dhereinafter. In each of FIGS. 12A to 12D, an upper view is a plan viewand a lower view is a sectional view.

In a structure in FIG. 12D, a difference from the structure in FIG. 11Dis that the two-dimensional lenses 612 have the concave shape.

As shown in FIGS. 12A and 12B, in the manufacturing method, first thefirst optical waveguide layer 611 and the second optical waveguide layer612 are formed such that their end surfaces are opposed mutually. Thesame steps as those in FIGS. 10A and 10B are applied as the formingsteps. The overlying cladding layers 611 c, 612 c to the underlyingcladding layers 611 a, 612 a are exposed from respective end surfaces ofthe formed opposing portions.

Then, as shown in FIG. 12C, respective end surfaces of the opticalwaveguide 611 and the two-dimensional lens 612 in the coupling portionare covered with the thin resin films (covering mediums) 611 d, 612 dhaving the intermediate refractive index n3 (ni1(nij) or ni2(nik))between the refractive index n1 (nc1(ncj), nc2(nck)) of the core layers611 b, 612 b of the optical waveguide 611 and the two-dimensional lens612 and the refractive index n2 (ni12(ni(j,k))) of the filling medium613, with which a portion between the opposing portions is filled later.

Then, as shown in FIG. 12D, the resin (filling medium) 613 with therefractive index n2 that is higher than the refractive index n3 of theresin films 611 d, 612 d, which are coated on the end surfaces, isselected, and the portion is filled therewith. Thus, the couplingstructural body of the optical parts, one of which is thetwo-dimensional concave lens, is completed.

As described, according to the third embodiment of the presentinvention, since the opposing portions between respective end surfacesof the two-dimensional lenses 601, 612 and the optical waveguides 602,611 in the coupling portion are filled with the filling mediums 603,613, the coupling loss and the reflection loss can be reduced. Inaddition, since their end surfaces are covered with the thin resin films601 d, 602 d, 611 d, 612 d and also the refractive index n3 is close tothe refractive indexes n1 of the core layers rather than the refractiveindexes n2 of the filling mediums 603, 613, the reflection loss can bereduced much more.

Here, the core layers having the same refractive index (n1) respectivelyare employed as the core layers of the first and second opticalwaveguide layers 601, 611, 602, 612. But the core layers with differentrefractive indexes (ncj, nck) may be employed. In this case, therefractive indexes ni(j,k) of the filling mediums 603, 613 and therefractive indexes nij, nik of the coating mediums 601 d, 611 d, 602 d,612 d are set as ncj>nij, nck>nik, nij, nik>ni(j,k) in the case of thetwo-dimensional convex lens, and also are set as ncj<nij, nck<nik, nij,nik<ni(j,k) in the case of the two-dimensional concave lens.

Fourth Embodiment

Next, a fourth embodiment of the present invention will be explainedwith reference to FIG. 13 and FIG. 14 hereunder.

An upper view of FIG. 13 is a plan view showing a coupling portionbetween two-dimensional convex lenses and the optical waveguidesaccording to the fourth embodiment, and a lower view of FIG. 13 is asectional view taken along a I—I line in the upper view.

If the resin (filling medium) 603 filled in the opposing portions, asexplained in the first to third embodiments, has the fluidity, it ispossible that such resin flows out to the periphery. Therefore, as shownin FIG. 13, a convex portion 604 for preventing the flowout of the resin603 to the peripheral portion may be formed to surround the opposingportions in FIG. 9C. As the convex portion 604, an insulating depositedfilm, coated film, or tape-like pasted film may be employed.

An upper view of FIG. 14 is a plan view showing another coupling portionbetween the two-dimensional convex lens and the optical waveguideaccording to the fourth embodiment, and a lower view of FIG. 14 is asectional view taken along a II—II line in the upper view.

Similarly, if the resin (filling medium) 603 filled in the opposingportions has the fluidity, as shown in FIG. 14, a stripe concave portion605 for storing the resin 603, which is going to flow out to theperipheral portion, therein may be formed to surround the opposingportions in FIG. 9C. Thus, the flowout of the resin 603 into theperipheral portion of the opposing portions can be prevented. As theconcave portion 605, a stripe-like grove formed by etching the overlyingcladding layers 601 c, 602 c, or the like may be employed.

In this case, in the above first to fourth embodiments, the presentinvention is applied to the coupling portion between the two-dimensionalconvex or concave lenses 601, 612 and the optical waveguides 602, 611.However, the present invention can be applied to the coupling portionbetween the opposing two-dimensional convex lenses or the couplingportion between the opposing two-dimensional concave lenses, as shown inFIGS. 15A and 15B.

Fifth Embodiment

Like the above first to fourth embodiments, if a laminated structureconsisting of the underlying cladding layer, the core layer, and theoverlying cladding layer is etched by the reactive ion etching, it ispossible that, as shown in FIG. 15B, an unevenness of about 100 nm isproduced on the formed end surface. FIG. 15A is a plan view showing thecoupling portion between such two-dimensional convex lenses 91, 92, andFIG. 15B is a sectional view taken along a III—III line in FIG. 15A. Thetwo-dimensional lens 91 made of a laminated structure consisting of anunderlying cladding layer 91 a, a core layer 91 b, and an overlyingcladding layer 91 c and the two-dimensional lens 92 made of a laminatedstructure consisting of an underlying cladding layer 92 a, a core layer92 b, and an overlying cladding layer 92 c are formed on a substrate 92a 0 to oppose their end surfaces to each other. FIG. 15B shows the statethat the unevenness is generated on respective end surfaces formed bythe reactive ion etching.

When the light propagates through interfaces of the uneven portions thathave different refractive indexes on both sides of the uneven portion,such light is scattered at the interfaces of the uneven portions. Thus,because of generation of such scattered light, the loss in the couplingstructural body of optical parts is increased.

In following embodiments, a structure that is effective to reduce thepropagation loss of the light such as the reflection loss, the couplingloss, etc. in such case will be explained.

FIG. 16 is a sectional view showing the coupling portion between theoptical waveguides as a part of the optical switch module having suchstructure, according to the fifth embodiment of the present invention.

In the fifth embodiment, optical waveguides 501 a, 502 a are patternedby the etching, but such optical waveguides 501 a, 502 a are not coveredwith the cladding layer. Respective end surfaces of the opticalwaveguides 501 a, 502 a in the opposing portions are covered with films(coating mediums) 501 b, 502 b made of the material with the samerefractive indexes ni1, ni2 (nij, nik) as the refractive indexes nc1,nc2 (ncj, nck) of the optical waveguides 501 a, 502 a. Then, a fillingmedium 503 made of the material with the low refractive index ni12(ni(j,k)) is filled in the concave portion of the opposing portions.

Therefore, since both end surfaces of the opposing portions becomesmooth, the scattering of the light, which propagates through theoptical waveguides 501 a, 502 a, at the end surfaces can be prevented.Therefore, the loss due to the reflection and the coupling loss can bereduced.

Also, since the opposing portions whose end surfaces become smooth bythe coating mediums 501 b, 502 b is filled with the filling medium withthe refractive index ni12 which is lower than the refractive indexesnc1, nc2 of the optical waveguides 501 a, 502 a, the loss due to thereflection can be reduced. Therefore, the propagation loss of the lightcan be reduced.

Sixth Embodiment

Next, a sixth embodiment of the present invention will be explained withreference to FIGS. 17A and 17B hereunder.

FIG. 17A is a plan view showing a collimator portion or a lightconverging portion of an optical switch module according to a sixthembodiment of the present invention, and is an enlarged plan view of thetwo-dimensional lens portion. FIG. 17B is a sectional view taken along aIV—IV line in FIG. 17A.

In the sixth embodiment, differences from the fifth embodiment are thatan underlying cladding layer 302 a and an overlying cladding layer 302 care provided under and on a core layer 302 b and two two-dimensionalconvex lenses 302 b are arranged at an interval to oppose to each other.In this case, the emissive-side end surface of the two-dimensionalconvex lens 302 b on the left side and the incident-side end surface ofthe two-dimensional convex lens 302 b on the right side are covered witha thin resin film (coating medium) 302 d made of the material with therefractive indexes nij, nik, which are the same as the refractiveindexes ncj, nck of the core layers 302 b, respectively. In addition,the opposing portions between the end surfaces of the two-dimensionalconvex lenses 302 b are filled with a filling medium 302 e made of thematerial with the refractive index ni22(ni(j,k)) which is lower than therefractive indexes ncj, nck of the core layers 302 b.

As described above, according to the optical switch module of the sixthembodiment, the end surfaces of the two-dimensional convex lenses 302 bformed by the reactive ion etching in the coupling portion are coveredwith the coating medium 302 d with the refractive indexes nij, nik,which are equal to the refractive indexes ncj, nck of the core layers302 b that are exposed from the end surfaces.

Since the refractive indexes nij, nik of the coating medium 302 d areequal to the refractive indexes ncj, nck of the core layers 302 b thatare exposed from the end surfaces, substantially smooth end surfaces ofthe two-dimensional convex lenses 302 b can be obtained by averaging theunevenness of the end surfaces by virtue of the coating medium 302 d.Therefore, the scattering of the light at the end surfaces of thetwo-dimensional lenses 302 b can be prevented, and thus the loss due tothe reflection and the coupling loss can be reduced.

Also, since the opposing portions whose end surfaces are made smooth bythe coating medium 302 d are filled with the filling medium with therefractive index ni22(ni(j,k)), which is lower than the refractiveindexes of the core layers 302 b, the loss due to the reflection can bereduced and also the light that is transmitted through thetwo-dimensional lenses can be collimated. Therefore, the propagationloss of the light can be reduced.

Seventh Embodiment

Next, a seventh embodiment of the present invention will be explainedwith reference to FIGS. 18A and 18B hereunder.

FIG. 18A is a plan view showing a part of an optical switch moduleaccording to a seventh embodiment of the present invention, and FIG. 18Bis a sectional view taken along a V—V line in FIG. 18A.

In the seventh embodiment, a difference from the fifth and sixthembodiments is that a structure in which the incident-side end surfaceof the optical waveguide (core layer) 403 b is smooth without unevennessis provided. Such structure can be obtained in the case thatphotosensitive material is employed as the material of the opticalwaveguide 403 b, and then the optical waveguide 403 b is formed by thepatterning using the photo process and only the two-dimensional lenses202 b are formed by the reactive ion etching, for example.

In this case, the emissive-side end surface of the two-dimensional lens202 b is covered with a resin film 212 with the refractive indexni2(nij), which is equal to the refractive index nc2(ncj) of the corelayer 202 b, to make the unevenness of the end surface smooth. However,since the incident-side end surface of the optical waveguide 403 b thatopposes to the two-dimensional lens 202 b is originally smooth withoutunevenness, such end surface is not covered with the coating medium,which has the same refractive index as that of the optical waveguide 403b to make the unevenness of the end surface smooth.

In addition, the opposing portions at which the end surface which ismade smooth by the coating medium 212, and the smooth end surface of theoptical waveguide 403 b are opposed to each other are filled with afilling medium 213 with the refractive index ni24(ni(j,k)) which islower than the refractive index of the core layer 202 b.

As described above, according to the optical switch module of theseventh embodiment, out of both end surfaces of the two-dimensionalconvex lens 202 b and the optical waveguide 403 b in the couplingportion, only the end surface of the two-dimensional convex lens 202 bformed by the reactive ion etching is covered with the coating medium212 that has the same refractive index ni2 as the refractive index nc2of the core layer 202 b that is exposed from the end surface.

In this manner, since the unevenness of the end surface that is formedby the etching is uniformized by using the coating medium 212, thesubstantially smooth end surface of the two-dimensional lens 202 b canbe obtained. Therefore, since both end surfaces of the coupling portionare made smooth, the scattering of the light caused at the end surfacesof the two-dimensional lens 202 b and the slab optical waveguide 403 bcan be prevented, and thus the loss due to the reflection and thecoupling loss can be reduced.

Also, since the opposing portions whose end surfaces are made smooth bythe coating medium 212 is filled with the filling medium 213 with therefractive index ni24(ni(j,k)) which is lower than the refractive indexnc2 of the core layer 202 b, the loss due to the reflection can bereduced and also the light that is transmitted through thetwo-dimensional lens 202 b can be collimated. Therefore, the propagationloss of the light can be reduced.

Eighth Embodiment

Next, an example of an optical switch module according to an eighthembodiment of the present invention is shown in FIG. 19 and FIGS. 20Aand 20B. FIG. 19 is a plan view showing the optical switch moduleaccording to the eighth embodiment. FIG. 20A is a plan view showing acoupling portion between an incident-side channel waveguide portion anda two-dimensional lens of a collimator portion according to the eighthembodiment, and FIG. 20B is a sectional view taken along a VI—VI line inFIG. 20A.

Assume that, as explained in FIG. 3, the measures are applied to thecoupling portions of respective optical parts of the incident-sidechannel waveguide portion 201, the collimator portion 202, the lightconverging portion 206, and the emissive-side channel waveguide portion207. Such configuration is shown in FIG. 19. In this case, in FIG. 19,the same references as those in FIG. 3 denote the same constituentelements in FIG. 3. In addition, in FIG. 19, a reference 200 denotes anincident-side optical fiber, and a reference 208 denotes anemissive-side optical fiber.

As shown in FIGS. 20A and 20B, the incident-side channel waveguideportion 201 has a laminated structure that consists of a plurality ofcore layers 201 b formed at an interval mutually to propagate the lightmainly, and cladding layers 201 a, 201 c formed on and under the corelayers 201 b and on the left/right sides thereof. The laminatedstructure constitutes the optical waveguides each having the core layer201 b as the center. The refractive indexes nu1(nuj or nuk), no1(noj ornok) of the cladding layers 201 a, 201 c are set lower than therefractive index nc1 (ncj) of the core layer 201 b such that the lightthat is propagated through the core layer 201 b does not leak out to thesurrounding portion. The incident-side end surface of the opticalwaveguide is covered with a coating medium 211 made of the materialhaving the refractive index ni1 (nij) that is identical to therefractive index nc1 of the core layer 201 b.

As shown in FIGS. 20A and 20B, the collimator portion 202 is constructedby the opposing two-dimensional convex lenses (collimator lenses) 202 b.Each of the opposing two-dimensional convex lenses 202 b has a laminatedstructure that consists of the core layer 202 b made of the materialwith the refractive index nc2 (ncj,nck), which is identical to therefractive index nc1 of the core layer 201 b in the incident-sidechannel waveguide portion 201, e.g., the quartz to propagate the lightmainly, and cladding layers 202 a, 202 c formed on and under the corelayers 202 b and on the left/right sides thereof. Then, theemissive-side end surface and the incident-side end surface of thetwo-dimensional lenses 202 b are covered with the coating medium 212made of the resin having the refractive index ni2 (nij,nik) that isidentical to the refractive index nc2 of the core layer 202 brespectively. In addition, as shown in FIG. 19 and FIGS. 20A and 20B, aportion between the emissive-side end surface and the incident-side endsurface of the opposing two-dimensional lenses 202 b is filled with thefilling medium 213 with the refractive index ni22(ni(j,k)). For example,the filling medium 213 is made of the material with the refractive indexni22, which is lower than the refractive index of the quartz, e.g., thefluororesin.

As shown in FIG. 19 and FIGS. 20A and 20B, the optical deflector element203 p constituting the incident-side optical deflector element portion203 is constructed by one or plural prism pairs. Then, one prism pair isconstructed by first and second upper electrodes formed on the laminatedstructure, which consists of a core layer 203 b made of the materialhaving the electrooptic effect, e.g., PZT and cladding layers 203 a, 203c formed on and under the core layer 203 b and on the left/right sidesthereof, and first and second lower electrodes formed under thelaminated structure. All the first and second upper electrodes and thefirst and second lower electrodes are shaped into a right triangle shape(wedge shape).

The first upper electrode and the first lower electrode are opposedmutually to put the laminated structure having the core layer 203 btherebetween. The first upper electrode and the second upper electrodeare arranged closely to oppose their hypotenuses mutually. The secondupper electrode and the second lower electrode are opposed mutually toput the laminated structure therebetween. In this case, the laminatedstructure having the core layer 203 b is common in respective prismpairs.

The common optical waveguide portion 204 has a laminated structure thatconsists of the slab waveguide (core layer) through which the lightpropagates mainly and the cladding layers formed around the slabwaveguide. In FIG. 19, an uppermost overlying cladding layer 204 c isshown.

As shown in FIG. 19, the optical deflector element 205 p of theemissive-side optical deflector element portion 205 is constructed byone or plural prism pairs, which is similar to the incident-side opticaldeflector element 203 p. Each prism pair is constructed by a pair offirst electrodes (the first upper electrode and the first lowerelectrode) formed to put the laminated structure, which has the corelayer and the cladding layers formed on and under the core layer and onthe left/right sides thereof, therebetween and a pair of secondelectrodes (the second upper electrode and the second lower electrode).In FIG. 19, an uppermost overlying cladding layer 205 c is shown.

As shown in FIG. 19, like the collimator portion 202, the convex lightconverging lenses 206 b are opposed to each other in the lightconverging portion 206. The portion of the convex light converging lens206 b has a laminated portion that consists of the core layer 206 b madeof the same material as the core layer 201 b, e.g., the quartz topropagate the light mainly and the cladding layers formed on and underthe core layer and on the left and right sides thereof. Then, the endsurfaces of the opposing light converging lenses are covered with aresin film (coating medium) 216 having the refractive indexni6(nij,nik), which is identical to the refractive index nc6(ncj,nck) ofthe core layer 206 b, respectively. A portion between the end surfacesof the opposing light converging lenses is filled with a filling medium217. For example, the filling medium 217 is formed of the materialhaving the refractive index ni66(ni(j,k)) that is lower than therefractive index of the quartz, e.g., the fluororesin.

As shown in FIG. 19, the emissive-side channel optical waveguide portion207 has the same laminated structure as the incident-side channeloptical waveguide portion 201, in which the channel optical waveguides207 b are arranged at an interval mutually in the same number as thechannel optical waveguides 201 b. The emissive-side end surface of thechannel optical waveguide 207 b is covered with a coating medium 218that is made of the material having the same refractive index ni7(nik)as the refractive index nc7(nck) of the core layer 207 b.

As described above, according to the optical switch module of the eighthembodiment, the end surfaces of respective coupling portions formed bythe reactive ion etching are covered with the coating mediums 211, 212,216, 218 having the refractive indexes ni1, ni2, ni6, ni7 (nij,nik),which are identical to the refractive indexes nc1, nc2, nc6, nc7(ncj,nck) of the core layers that are exposed from the end surfaces.

Since the refractive index nij or nik of the coating medium is equal tothe refractive index ncj or nck of the core layer that is exposed fromthe end surface, such coating medium can be regarded as the core layerwith respect to the propagation of the light. Therefore, even if theunevenness is generated on the end surface of the optical waveguide,which is exposed from the opposing portions in the coupling portion bythe reactive ion etching or the like, the substantially smooth endsurface of the optical waveguide can be obtained by uniformizing theunevenness on the end surface with the coating medium. It results inpreventing the scattering of the light, which propagates through theoptical waveguide, at the end surface, and thus it leads to reduction ofthe loss due to the reflection and the coupling loss.

Also, in the collimator portion 202 and the light converging portion206, the opposing portions whose end surfaces become smooth by thecoating mediums 212, 216 is filled with the filling medium 213, 217 withthe refractive index ni22, ni66(ni(j,k)) which is lower than therefractive index of the core layer. It leads to reduction of the lossdue to the reflection can be reduced, and thus the propagation loss ofthe light.

In this case, in the eighth embodiment, the coupling structural body ofoptical parts of the present invention is provided to the collimatorportion 202 and the light converging portion 206. As the case may be,the coupling structural body of optical parts may be provided to atleast any one of these coupling portions.

The present invention is explained in detail with reference torespective embodiments as above. But the present invention is notlimited to the examples that are particularly given in the aboveembodiments, and modifications of the above embodiment not to departfrom the gist of the present invention are contained in the scope of thepresent invention.

As described above, according to the coupling structural body of opticalparts of the present invention, the first and second optical waveguidesare arranged to oppose their end surfaces from which the overlyingcladding layer to the underlying cladding layer are exposed, and aportion between the mutual end surfaces is filled with the fillingmedium with the refractive index ni(j,k). Therefore, if the refractiveindex ni(j,k) is selected appropriately, the loss can be reduced incontrast to the case where a portion between the end surfaces is filledwith the air layer (ni(i,k)=1), and also the margin can be delivered tothe interval between the end surfaces.

Also, the above structure is constructed by forming the first and secondoptical waveguides, that are opposed in their end surfaces from whichthe overlying cladding layer to the underlying cladding layer areexposed, by steps of laminating the overlying cladding layer, the corelayer, and the underlying cladding layer, and then etching continuouslythe overlying cladding layer to the underlying cladding layer, followedby filling the portion between the mutual end surfaces with the fillingmedium.

Therefore, since the polishing step required in the prior application isnot needed, simplification of the steps can be attained. Also, the filmthicknesses of the core layer, etc. are decided at the time of filmformation, control of the film thicknesses can be facilitated.

Also, according to another coupling structural body of optical parts ofthe present invention, the end surfaces formed by the etching arecovered with the coating medium with the refractive index nij or nikthat is equal to the refractive index ncj or nck of the core layer thatis exposed from the end surface.

Since the refractive index nij or nik of the coating medium is equal tothe refractive index ncj or nck of the core layer that is exposed fromthe end surface, such coating medium can be regarded as the core layerwith respect to the propagation of the light. Therefore, even if theunevenness is generated on the end surfaces of the first or secondoptical waveguide in the opposing portions by the etching, thesubstantially smooth end surface of the optical waveguide can beobtained by uniformizing the unevenness on the end surface by means ofthe coating medium. It results in preventing the scattering of thelight, which propagates through the optical waveguide, at the endsurface, and thus in reducing the loss due to the reflection and thecoupling loss.

Also, the area that is next to the two-dimensional convex lenses whoseend surfaces are made smooth by the coating mediums is filled with thefilling medium with the refractive index ni(j,k), which is lower thanthe refractive index of the core layer. It leads to reducing the lossdue to the reflection, and to collimating the light that is transmittedthrough the two-dimensional lenses. It results in reduction of thepropagation loss of the light.

Ninth Embodiment

FIG. 22 is a plan view showing an example of a configuration of anoptical switch module having a two-dimensional lens array according to aninth embodiment of the present invention.

In FIG. 22, an optical switch 700 for switching optical signals on8-input channels into 8-output channels as a whole to output them isshown as an example. This optical switch 700 is composed of aninput-side optical fiber array 710, an optical input waveguide portion720, a collimator portion 730, an input-side optical deflector elementportion 740, a common optical waveguide 750, an output-side opticaldeflector element portion 760, a light converging portion 770, anoptical output waveguide portion 780, and an output-side optical fiberarray 790. In this case, in the optical switch 700, the collimatorportion 730 and the light converging portion 770 correspond to atwo-dimensional lens array of the present invention.

The input-side optical fiber array 710 is provided with a plurality ofoptical fibers 711 that correspond to respective input channels. Theoptical input waveguide portion 720 is provided with a plurality ofoptical input waveguides 721 that correspond to respective opticalfibers 711. The collimator portion 730 are provided with a plurality ofcollimator lenses 731 that correspond to respective optical inputwaveguides 721. The input-side optical deflector element portion 740 isprovided with a plurality of input-side optical deflector elements 741that correspond to respective collimator lenses 731.

The optical signals are input into the input-side optical fiber array710 from the outside via the optical fibers 711. Respective opticalfibers 711 are aligned on the substrate 712. A plurality of V-shapedgrooves are formed on a surface of the substrate 712. The optical fibers711 are fitted into the grooves respectively. Emissive ends of theoptical fibers 711 are connected to incident ends of respective opticalinput waveguides 721 in the optical input waveguide portion 720.

In the optical input waveguide portion 720, respective optical inputwaveguides 721 receive the optical signals from the optical fibers 711on the incident side and then emit these optical signals to respectivecollimator lenses 731 in the collimator portion 730. In the collimatorportion 730, respective collimator lenses 731 convert the opticalsignals, which are emitted from the optical input waveguides 721 on theincident side to spread radially, into parallel lights individually, andthen allow the optical signals to be incident on respective input-sideoptical deflector elements 741 on the emissive side. In this case, adetailed structure of the collimator portion 730 will be explained withreference to FIG. 21 and FIGS. 23A and 23B later. In the input-sideoptical deflector element portion 740, respective input-side opticaldeflector elements 741 change the propagation directions of the opticalsignals emitted from the corresponding collimator lenses 731 on theincident side, and then emit such optical signals to the output-sideoptical deflector element portion 760 via the common optical waveguide750.

The common optical waveguide 750 is constructed by slab waveguides, andtransmits the optical signal that is emitted from the input-side opticaldeflector element portion 740 to the output-side optical deflectorelement portion 760.

In the output-side optical deflector element portion 760, a plurality ofoutput-side optical deflector elements 761 that correspond to respectiveoutput channels are provided. In the light converging portion 770, aplurality of light converging lenses 771 that correspond to respectiveoutput-side optical deflector elements 761 are provided. In the opticaloutput waveguide portion 780, a plurality of optical output waveguides781 that correspond to respective light converging lenses 771 areprovided. In the output-side optical fiber array 790, a plurality ofoptical fibers 791 that correspond to respective optical outputwaveguides 781 are provided.

In the output-side optical deflector element portion 760, respectiveoutput-side optical deflector elements 761 change the propagationdirections of the optical signals, which are input from respectiveinput-side optical deflector elements 741 via the common opticalwaveguide 750, and then cause the optical signals to input intorespective light converging lenses 771 on the emissive side. In thelight converging portion 770, respective light converging lenses 771focus the optical signals, which are fed from respective output-sideoptical deflector elements 761, onto respective optical outputwaveguides 781 on the emissive side. In this case, the light convergingportion 770 has the similar structure to the collimator portion 730, anddetails of the inner structure will be described later. In the opticaloutput waveguide portion 780, respective optical output waveguides 781emit the optical signals being received from respective light converginglenses 771 to respective optical fibers 791 on the emissive sideindividually.

In the output-side optical fiber array 790, the respective opticalfibers 791 are aligned on a substrate 792. Like the input-side opticalfiber array 710, a plurality of V-shaped grooves are formed on a surfaceof the substrate 792. The optical fibers 791 are fitted into the groovesrespectively. Incident ends of the optical fibers 791 are connected toemissive ends of respective optical output waveguides 781, and then theoptical signals from respective optical output waveguides are output tothe outside.

Such optical switch 700 will be operated as follows.

The optical signals that are input into the optical input waveguides 721from respective optical fibers 711 are converted into parallel lights bythe collimator lenses 731, and then are input into the input-sideoptical deflector elements 741. When the voltages applied to the prismelectrodes are controlled, the input-side optical deflector elements 741change arbitrarily the propagation direction of the incident opticalsignals and then cause such optical signals to input into anyoutput-side optical deflector element 761 in the output-side opticaldeflector element portion 760 via the common optical waveguide 750.

When the voltages applied to the prism electrodes are controlled, theoutput-side optical deflector elements 761 change the propagationdirections of the optical signals such that the incident optical signalsare input into the corresponding light converging lenses 771 on theemissive side. The optical signals that are incident on the lightconverging lenses 771 are focused and input onto the correspondingoptical output waveguides 781 on the emissive side. The optical signalsare output from the optical output waveguides 781 to the outside throughthe optical fibers 791.

Accordingly, in the above optical switch 700, if the voltages that areapplied to the input-side optical deflector elements 741 and theoutput-side optical deflector elements 761 respectively are controlled,respective optical signals supplied from a plurality of input channelscan be switched to any output channels and then be output thereto.

Next, configurations of the collimator portion 730 and the lightconverging portion 770 in the above optical switch 700 will be explainedin detail hereunder.

FIG. 21 is a plan view showing a configuration of the collimator portion730 and its peripheral portion of the two-dimensional lens arrayaccording to the ninth embodiment of the present invention. Also, FIGS.23A and 23B are sectional views showing the configurations of thecollimator portion 730 and its peripheral portion respectively.

FIG. 21 shows an enlarged view of a part of the collimator portion 730and its peripheral portion in the optical switch 700 shown in FIG. 22.Also, FIG. 23A shows a sectional view taken along a VII—VII line in FIG.21, and FIG. 23B shows a sectional view taken along a VIII—VIII linetherein.

As shown in FIG. 21 and FIGS. 23A and 23B, the optical input waveguideportion 720, the collimator portion 730, the input-side opticaldeflector element portion 740, and the common optical waveguide 750 areprovided on the same substrate 701.

The collimator portion 730 has waveguide layers 732 as the slab opticalwaveguides on which the optical signals are incident from the opticalinput waveguides 721, and air-gap filling layers 733 which are formed bybeing filled with a medium with a refractive index that is differentfrom the waveguide layers 732. The air-gap filling layers 733 are formedby filling the air-gap region formed by removing the core layer and theoverlying/underlying cladding layers of the waveguide layer 732 with thefluororesin for preventing the diffusion of light. Here, theoverlying/underlying cladding layers of the waveguide layer 732 areformed of the quartz and the core layers thereof are formed of thequartz into which Ge is doped to enhance the refractive index. Therefractive index of the fluororesin in the air-gap filling layers 733 isset slightly lower than them.

Then, the end surface of the waveguide layer 732 opposing to the air-gapfilling layers 733 has its center on an optical axis of the opticalsignal from each optical input waveguide 721. Here, such end surface isshaped into a circular cylindrical shape, for example and is used as alens curved surface 734 of the collimator lens 731 acting as thetwo-dimensional lens. According to such structure, in the collimatorlens 731, the optical signal that propagates through the waveguide layer732 from the optical input waveguide 721 to spread radially is convertedinto the parallel light by the lens curved surface 734, and then isoutput to each input-side optical deflector element 741 in theinput-side optical deflector element portion 740.

In this case, as shown in FIGS. 23A and 23B, the input-side opticaldeflector element portion 740 arranged on the emissive side of thecollimator portion 730 has a structure such that slab optical waveguides743 made of the electrooptic crystal are put between the prism electrode744 and the conductive substrate 742 which are oppose to each otherthrough the slab optical waveguides 743. In this input-side opticaldeflector element portion 740, if the voltage is applied between theprism electrode 744 and the conductive substrate 742, the refractiveindex of the slab optical waveguide 743 in the region that is interposedtherebetween is changed. Thus, the propagation direction of the opticalsignal that is input from the collimator lens 731 is switched in theslab optical waveguide 743.

Incidentally, in the collimator portion 730, the optical signal that isinput from the optical input waveguide 721 propagates through thewaveguide layer 732 to spread radially. At this time, most part of thepropagated light is passed through the lens curved surface 734 and isconverted into the parallel light. In other words, in the waveguidelayer 732, the lens curved surface 734 can correctly collimate only thelight being propagated through the predetermined sectorial region, whichspreads toward the lens curved surface 734 from the emissive end of theoptical input waveguide 721 as the center point. However, since actuallythe light being propagated through the outside of this region ispresent, in some cases such light is diffused at the end portion of thelens curved surface 734, or such light is output directly to theneighboring lens curved surface 734.

For this reason, in the present invention, a light absorbing body 735 isarranged on both sides of the propagation region of the light, which isincident on each lens curved surface 734, in the waveguide layer 732. Inthe present embodiment, since the neighboring lens curved surfaces 734are formed to contact to each other, the light absorbing body 735 isprovided between the boundary of the lens curved surfaces and theincident end of the waveguide layer 732 one by one. Also, as shown inFIGS. 23A and 23B, for example, the light absorbing body 735 is providedto pass through the core layer and the overlying/underlying claddinglayers of the waveguide layer 732. As the material of the lightabsorbing body 735, the black resin material into which the carbon isdispersed, for example, is employed.

The light that propagates through the region in which the light is notcorrectly collimated by the lens curved surface 734 can be absorbed bysuch light absorbing body 735, and thus the propagation of the light tothe neighboring lens curved surface 734 can be prevented. Thus, itprevents the generation of the crosstalk of the optical signals, whichare output from the collimator portion 730, between the neighboringchannels.

Also, it is desired that the light absorbing body 735 should be formedto separate its end portion in the emissive direction from the endportion of each lens curved surface 734. In addition, it is desired thatthe light absorbing body 735 should be formed to separate its endportion in the incident direction from the incident end of the waveguidelayer 732. Accordingly, as described later, if the core layer and thecladding layers, which correspond to the area into which the lightabsorbing body 735 is provided, are removed from the waveguide layer 732as the uniform slab waveguide and then the removed area is filled withthe resin material and then the resin material is solidified, the lightabsorbing body 735 can be easily provided. In this case, it is desiredthat, in order to prevent the leakage of the light into the neighboringlens curved surface 734 and suppress an amount of generation of thecrosstalk, both respective areas in which the light absorbing body 735is provided and respective intervals between the end portions of thelens curved surface 734 and the incident ends of the waveguide layers732 should be reduced as small as possible.

Also, in the present embodiment, as an example, the light absorbing body735 is formed to have a circular shape or an elliptic shape when viewedfrom the top. According to such shape, for example, the light beingemitted from the optical input waveguide 721 can be prevented from beingscattered at the side surface of the light absorbing body 735, etc. Inthis case, a length of the circular or elliptic light absorbing body 735in the width direction (the vertical direction in FIG. 21) is set suchthat the light being output from the optical input waveguide 721 can beinput into at least an inside of the corresponding lens curved surface734. In addition, it is desired that the width of the light absorbingbody 735 should be set in answer to the width that is required for thecollimated light emitted from the lens curved surface 734.

Next, FIG. 24 is a plan view showing configurations of the lightconverging portion 770 and its peripheral portion.

FIG. 24 shows an enlarged view of a part of the light converging portion770 and its peripheral portion in the optical switch 700 shown in FIG.22. The output-side optical deflector element portion 760, the lightconverging portion 770, and the optical output waveguide portion 780,shown in FIG. 24, are provided on the same substrate 701 (not shown) onwhich the above optical input waveguide portion 720, etc. are provided.

Also, the output-side optical deflector element portion 760, the lightconverging portion 770, and the optical output waveguide portion 780have the same structures as those of the input-side optical deflectorelement portion 740, the collimator portion 730, and the optical inputwaveguide portion 720 which are provided opposedly to put the commonoptical waveguide 750 therebetween, respectively.

More particularly, the light converging portion 770 has waveguide layers772 as the slab optical waveguides that propagate the optical signals tothe optical output waveguides 781 respectively, and air-gap fillinglayers 773 which are formed by filling with the medium with a refractiveindex that is different from the waveguide layers 772. Also, in theair-gap filling layers 773, the air-gap region which is formed byremoving the core layer and the overlying/underlying cladding layers ofthe waveguide layer 772 is filled with the fluororesin for preventingthe diffusion of light. Here, like the collimator portion 730, theoverlying/underlying cladding layers of the waveguide layer 772 areformed of the quartz and the core layers are formed of the quartz intowhich Ge is doped to enhance the refractive index. The refractive indexof the fluororesin in the air-gap filling layers 773 is set slightlylower than them.

Then, the end surface of the waveguide layer 772 opposing to the air-gapfilling layers 773 is shaped into the circular cylindrical surface thathas the center on an optical axis of the optical signal from eachoptical input waveguide 781. Here, this end surface is shaped into alens curved surface 774 of the light converging lens 771 acting as thetwo-dimensional lens. According to such structure, in respective lightconverging lenses 771, the optical signals, that are emitted fromrespective output-side optical deflector elements 761 and passed throughthe air-gap filling layers 773, propagate through the waveguide layers772 from the lens curved surfaces 774 and then are focused on theincident ends of respective optical output waveguides 781 and inputtherein.

Also, like the collimator portion 730, in the waveguide layer 772, alight absorbing bodies 775 are arranged on both sides of the propagationregion of the lights, which propagate from respective lens curvedsurfaces 774 to focus onto the optical output waveguide 781. Forexample, the light absorbing body 775 is provided to pass through thecore layer and the overlying/underlying cladding layers of the waveguidelayer 772. As the material of the light absorbing body 775, the blackresin material into which the carbon is dispersed, for example, isemployed.

In this light converging portion 770, the optical signals being inputfrom the respective output-side optical deflector elements 761 are thesubstantially parallel light. However, because of errors of respectiveelements of this optical switch 700 at the time of manufacture,variation in the performance of the output-side optical deflectorelements 761, etc., in some cases the width of the light that passesthrough the lens curved surface 774 (the length in the verticaldirection in FIG. 24) is not always kept constant. In such case, all thelights that are passed through the lens curved surface 774 are notfocused onto the incident ends of the optical output waveguide 781, andextra lights are emitted to the surrounding area of the optical outputwaveguide 781. Thus, in some cases this light exerts a bad influence onthe optical signal that propagates through the optical output waveguide781. Otherwise, the extra lights are reflected by the end surface of thewaveguide layer 772 on the emissive side to return to the inside of thelight converging portion 770 and then to input into the neighboring lenscurved surface 774. Thus, in some cases the quality of the opticalsignal is possible to be deteriorated.

As the measure for this, the light absorbing bodies 775 are arranged onboth sides of the propagation area of the optical signal in the lightconverging portion 770. It can absorb the extract light that propagatesin the area in which the light is not correctly converged by the lenscurved surface 774, and thus It results in reducing the noise componentcontained in the optical signal that is incident on the optical outputwaveguide 781, etc. Therefore, the quality of the propagated opticalsignal can be enhanced.

As described above, the present invention leads to realization of thehigh-performance optical switch in which the crosstalk between thechannels and the noises in the optical signal are reduced.

Next, a method of manufacturing the above optical switch 700 will beexplained hereunder.

FIGS. 25A, 25B, and 25C are views for explaining the method ofmanufacturing the optical switch 700. In this case, FIGS. 25A, 25B, and25C show a cross section of the portion of the optical switch 700, whichcorresponds to FIG. 23B, respectively.

The above optical switch 700 has a structure such that the optical inputwaveguide portion 720, the collimator portion 730, the common opticalwaveguide 750, the light converging portion 770, and the optical outputwaveguide portion 780 are formed integrally on the substrate 701, thenthe input-side optical deflector element portion 740 and the output-sideoptical deflector element portion 760 are mounted on the substrate 701,and then the input-side optical fiber array 710 and the output-sideoptical fiber array 790 are connected.

As shown in FIG. 25A, first a uniform slab optical waveguide 702 isformed on the substrate 701. As the substrate, the quartz, the Si wafer,or the like is used. In the case of the quartz, this substrate 101 alsofunctions as the underlying cladding layer of the slab optical waveguide702 formed thereon. The core layer is formed of the quartz, whoserefractive index is enhanced by diffusing Ge thereinto, on the substrate101 and then the overlying cladding layer is formed of the quartzthereon. The core layer and the overlying cladding layer are formed bythe MOCVD (Metal Organic Chemical Vapor Deposition) method, or the like,for example.

Then, an etching mask made of a metal film is formed on a surface of theoverlying cladding layer of the slab optical waveguide 702 by thephotolithography method and the sputtering method. Then, the overlyingcladding layer and the core layer are etched collectively by thereactive ion etching (RIE) using the fluorine gas, or the like whileemploying the etching mask. Thus, as shown in FIG. 25B, not only theoptical input waveguides 721 and the common optical waveguide 750 areformed, but also air gaps 733 a, the waveguide layers 732, the lenscurved surfaces 734, and filling portions 735 a for being filled withthe material of the light absorbing body 735, in the collimator portion730 and mounting portions 740 a, on which the input-side opticaldeflector element portion 740 is mounted, are formed.

In this case, for example, if a width of the core layer is set to 5 μmand a pitch between the optical input waveguides 721 is set to 2.5 mm, asize of the filling portion 735 a is decided so that the width of theoptical signal that is collimated by the lens curved surface 734 is setto 0.6 mm.

Here, the area of the filling portion 735 a of the light absorbing body735 is formed away from the end portion of the lens curved surface 734and the incident end of the waveguide layer 732. Thus, as shown in FIG.25B, the filling portion 735 a of the light absorbing body 735 is shapedinto a concave shape that is surrounded by the waveguide layer 732.

Although not shown, the air gaps, the waveguide layers 772, the lenscurved surfaces 774, and filling portions for being filled with thelight absorbing body 775, in the light converging portion 770 andmounting portions, on which the output-side optical deflector elementportion 760 is mounted, are formed simultaneously on the substrate 701at the time of the above collective etching.

Then, electrodes 740 b that are connected to the prism electrodes 744 ofthe respective input-side optical deflector elements 741 are provided tobottom surfaces of the mounting portions 740 a, on which the input-sideoptical deflector element portion 740 is mounted. These electrodes 740 bare formed by coating a resist on the bottom surfaces of the mountingportions 740 a, then applying the patterning to the resist, thenlaminating a titanium film by the sputtering method, and then laminatinga platinum film by the lift-off method.

Here, the input-side optical deflector element portion 740 ismanufactured as follows. The input-side optical deflector elementportion 740 has a structure such that the slab optical waveguides 743are formed on the conductive substrate 742 and then the prism electrodes744 are provided thereon. As the conductive substrate 742, STO (SrTiO₃)single crystal as the ferroelectric substance, into which Nb is doped toprovide the conductivity, is employed. Also, in the slab opticalwaveguides 743, PZT (Pb(Zr_(y)Ti_(1-y)O₃)) and PLZT(Pb_(x)La_(1-x)(Zr_(y)Ti_(1-y)O₃)) are used as the core layer and theoverlying/underlying cladding layers respectively. This slab opticalwaveguide 743 is formed by laminating PZT, PLZT, and PZT on theconductive substrate 742 in this order. For laminating them, theheteroepitaxial growth is implemented by the sol-gel method, the PLD(Pulsed Laser Deposition) method, the MOCVD method, or the like.

Then, the triangular prism electrodes 744 are formed in parallelalignment on the surfaces, which oppose to the conductive substrate 742of the slab optical waveguide 743, as many as the input channels. Theseprism electrodes 744 are formed by forming a film by thephotolithography method using a metal such as a platinum film, or thelike, and then polishing the film into a predetermined size.

In this case, the output-side optical deflector element portion 760 hasthe totally same structure as that of the input-side optical deflectorelement portion 740, and is manufactured by the same steps.

Then, the input-side optical deflector element portion 740 and theoutput-side optical deflector element portion 760 are mounted on thesubstrate 701. In the case of the input-side optical deflector elementportion 740, as shown in FIG. 25B, the input-side optical deflectorelement portion 740 is fixed by connecting the prism electrodes 744 andthe corresponding electrodes 740 b on the substrate 701 via the solderbump, or the like while directing its surface, on which the prismelectrodes 744 are provided, toward the substrate 701 side. At thistime, the alignment between the optical waveguides positioned on theincident side and the emissive side must be executed precisely. In thiscase, the output-side optical deflector element portion 760 is mountedsimilarly onto the substrate 701.

Then, as shown in FIG. 25C, the air gaps 733 a between the waveguidelayers 732 in the collimator portion 730 and the input-side opticaldeflector element portion 740 is filled with the fluororesin having thethermosetting property. The fluororesin has the refractive index that isslightly lower than the quartz constituting the waveguide layers 732.The air-gap filling layers 733 are formed by heating the fillingfluororesin to solidify. At this time, the air-gap filling layers 773 inthe light converging portion 770 are also formed simultaneously by thesame method.

Meanwhile, the air gaps may be used, as they are, not to be filled withthe fluororesin. In this case, since the refractive index of the air isdifferent from that of the fluororesin, a curvature of the lens curvedsurface must be changed. However, in the case of the air gaps, since thelight that passed through the lens curved surface is ready to scatter,it is desired that it should be filled with the material for preventingthe scattering of light by the fluororesin etc.

Then, as shown in FIG. 25C, the filling portions 735 a of the collimatorportion 730 is filled with the material of the light absorbing body 735by the screen printing method. As the material, the black resin materialinto which the carbon is dispersed, for example, is employed, and issolidified after the filling. Here, since the surrounding area of thefilling portion 735 a is formed like the concave shape that issurrounded by the waveguide layer 732, materials of the light absorbingbody 735 and the air-gap filling layer 733 are not mixed together.Therefore, both the light absorbing body 735 and the air-gap fillinglayer 733 can be easily formed by being filled with respective materialsinto the concave areas merely. Although not shown, at this time, thefilling portions that are formed in the light converging portion 770 arealso filled with the material of the light absorbing body 735.

According to the above method of manufacturing the optical switch 100,the uniform slab optical waveguide 702 is formed on the common substrate701 and then the filling portions of the light absorbing body 735 aswell as the optical input waveguides, the air gaps, etc. can be formedcollectively by etching the slab optical waveguide 702. Therefore, thefilling portions of the light absorbing body 735 can be formed not tolargely change the conventional manufacturing steps. Also, since thefilling portion is formed as the area that is surrounded by thewaveguide layer, the light absorbing body 735 can be formed easily bymerely injecting the material into this area.

As a result, according to the present invention, the optical switch inwhich the crosstalk between the channels can be reduced and the qualityof the propagated optical signal can be improved can be manufacturedeffectively.

In the above ninth embodiment, in the collimator portion 730 and thelight converging portion 770, the material whose refractive index islower than that of the waveguide layer is employed for the air-gapfilling layer. But the material such as the epoxy resin, or the like,which has the high refractive index, can be employed for the air-gapfilling layer. In this case, the shape of the lens curved surface mustbe changed from the concave lens to the convex lens.

Also, in the collimator portion 730 and the light converging portion770, respective lens shapes of the collimator lens 731 and the lightconverging lens 771 are formed as the circular cylindrical shape. Butthe aspherical lens may be applied.

In addition, in the collimator portion 730 and the light convergingportion 770, the lens curved surfaces are provided only on one of theincident side and the emissive side to put the air-gap filling layertherebetween respectively. But such lens curved surfaces may be providedon the incident side and the emissive side to oppose to each otherrespectively. In this case, for example, in the case of the collimatorportion 730, the waveguide layer should be arranged not only on theincident side of the air-gap filling layer 733 but also between theemissive side and the mounting portion of the input-side opticaldeflector element portion 740. Similarly, in the case of the lightconverging portion 770, the waveguide layer should be arranged betweenthe incident side of the air-gap filling layer 773 and the mountingportion of the emissive-side optical deflector element portion 760.

Also, in the above ninth embodiment, in both the collimator portion 730and the light converging portion 770, the air-gap filling layer isprovided integrally to all channels by jointing the neighboring lenscurved surfaces. The present invention is not limited to this. Theneighboring lens curved surfaces may be separated. In this case, theair-gap filling layers are provided as the areas, which are surroundedby the waveguide layer, individually in response to respective lenscurved surfaces.

Also, in the above ninth embodiment, the optical input waveguides 721are connected to the collimator portion 730 and the optical signals areinput thereto. However, for example, the optical fibers may be directlyconnected to the incident ends of the waveguide layers 732 in thecollimator portion 730. Similarly, the optical fibers may be directlyconnected to the emissive ends of the waveguide layer 772 in the lightconverging portion 770.

Also, in the above ninth embodiment, the example in which thetwo-dimensional lens array is applied to the optical switch as thecollimator portion and the light converging portion is shown. However,the present invention is not limited to this. The present invention maybe applied other optical devices having the area in which the opticalsignals propagate in parallel through a plurality of channels.

As described above, according to the two-dimensional lens array of thepresent invention, for example, if the optical signal propagates throughthe slab optical waveguide to the lens curved surface, the lightabsorbing body is provided in the slab optical waveguide on both sidesof the propagation area of the optical signal, and therefore the extralight that is not precisely incident on the lens curved surface and thescattered light from the end portion of the lens curved surface, etc.can be absorbed by such light absorbing body. Therefore, the incidenceof the light into the neighboring lens curved surface can be preventedand also generation of the crosstalk between the neighboring channelscan be reduced. Also, if the optical signal is incident on the slaboptical waveguide from the lens curved surface, the extra light thatpassed through the lens curved surface and then propagates through theoutside of the predetermined area of the emissive end can be absorbed bythe light absorbing body. Therefore, only the necessary light is emittedfrom the emissive side, and thus the quality of the propagated opticalsignal can be enhanced.

Also, according to the optical switch of the present invention, sincethe first light absorbing body is provided on both sides of thepropagation area of the optical signal from the optical input waveguideto the corresponding collimator lens, the extra light that is notprecisely incident on the collimator lens and the scattered light fromthe end portion of the lens curved surface of the collimator lens, etc.can be absorbed by such first light absorbing body. Therefore, theincidence of the light into the neighboring lens curved surface can beprevented and also the generation of the crosstalk between theneighboring channels can be reduced. Also, since the second lightabsorbing body is provided on both sides of the propagation area of theoptical signal from the light converging lens to the correspondingoptical output waveguide, the extra light that is not precisely incidenton the lens curved surface can be absorbed by such second lightabsorbing body. Therefore, only the necessary light is emitted from theoptical output waveguide, and thus the quality of the propagated opticalsignal can be enhanced.

1. An optical switch module comprising: a collimator portion forcollimating a plurality of optical signals individually bytwo-dimensional lenses respectively; a plurality of first opticaldeflector elements for switching propagation directions of the opticalsignals, which passed through the collimator portion, individually byusing an electrooptic effect respectively; a common optical waveguidefor propagating the optical signals that passed through the plurality offirst optical deflector elements respectively; a plurality of secondoptical deflector elements for switching the propagation directions ofthe optical signals, which passed through the common optical waveguide,individually by using the electrooptic effect respectively; and a lightconverging portion for converging the optical signals, which passedthrough the plurality of second optical deflector elements, individuallyby the two-dimensional lenses respectively; wherein at least any one ofthe collimator portion and the light converging portion is provided withthe coupling structural body of optical parts, constructed by arranginga first optical waveguide in which an underlying cladding layer with arefractive index nuj, a core layer with a refractive index ncj, and anoverlying cladding layer with a refractive index noj are laminated, anda second optical waveguide in which an underlying cladding layer with arefractive index nuk, a core layer with a refractive index nck, and anoverlying cladding layer with a refractive index nok are laminated, arearranged to oppose end surfaces, from which the overlying cladding layerto the underlying cladding layer are exposed, to each other, and thenfilling a portion between mutual end surfaces with a filling medium witha refractive index ni(j,k), whereby at least one end surface of both endsurfaces is formed as a two-dimensional lens and a light propagates fromone optical waveguide to other optical waveguide through the fillingmedium.
 2. An optical switch module according to claim 1, whereinrefractive indexes of core layers constituting the first opticaldeflector elements and the second optical deflector elements are sethigher than any of refractive indexes of core layers in the collimatorportion, the common optical waveguide, and the light converging portion.3. An optical switch module comprising: a collimator portion forcollimating a plurality of optical signals individually bytwo-dimensional lenses respectively; a plurality of first opticaldeflector elements for switching propagation directions of the opticalsignals, which passed through the collimator portion, individually byusing an electrooptic effect respectively; a common optical waveguidefor propagating the optical signals that passed through the plurality offirst optical deflector elements respectively; a plurality of secondoptical deflector elements for switching the propagation directions ofthe optical signals, which passed through the common optical waveguide,individually by using the electrooptic effect respectively; and a lightconverging portion for converging the optical signals, which passedthrough the plurality of second optical deflector elements, individuallyby the two-dimensional lenses respectively; wherein the collimatorportion, the first optical deflector elements, the common opticalwaveguide, the second optical deflector elements, and the lightconverging portion have an optical waveguide respectively, and at leastany one of the collimator portion and the light converging portion isprovided with a coupling structural body of optical parts in which afirst optical waveguide having at least a core layer with a refractiveindex ncj and a second optical waveguide having at least a core layerwith a refractive index nck are arranged to oppose end surfaces to eachother, any one of the end surfaces of the first optical waveguide andthe second optical waveguide is formed by etching, and the end surfaceformed by the etching is covered with a surface smoothing coating mediumwith a refractive index nij or nik that is respectively equal to arefractive index ncj or nck of the core layer that is exposed from theend surface.
 4. An optical switch module according to claim 3, whereinrefractive indexes of core layers constituting the first opticaldeflector elements and the second optical deflector elements are sethigher than any of refractive indexes of core layers in the collimatorportion, the common optical waveguide, and the light converging portion.